Security World: [NT] Vulnerabilities in MSDTC and COM+ Allows Remote Code Execution (MS05-051)

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Vulnerabilities in MSDTC and COM+ Allows Remote Code Execution (MS05-051)
------------------------------------------------------------------------

SUMMARY

Multiple vulnerabilities have been discovered in Windows' MSDTC and COM+,
the following advisory summarizes 4 of them.

DETAILS

Affected Software:
* Microsoft Windows 2000 Service Pack 4 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=4E5B96D8-BA74-4008-80D9-922364ABC6AC> Download the update
* Microsoft Windows XP Service Pack 1 and Microsoft Windows XP Service
Pack 2 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=20F79CE7-D4DB-42D7-8E57-58656A3FB2F7> Download the update
* Microsoft Windows XP Professional x64 Edition -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=A6EC1352-042E-4FFB-B379-0E1C06AB9DBE> Download the update
* Microsoft Windows Server 2003 and Microsoft Windows Server 2003 Service
Pack 1 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=CA202CCC-792E-4462-9A2F-A20D1F8607F7> Download the update
* Microsoft Windows Server 2003 for Itanium-based Systems and Microsoft
Windows Server 2003 with SP1 for Itanium-based Systems -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=554A86A5-0B03-4CA9-A32D-642E40570424> Download the update
* Microsoft Windows Server 2003 x64 Edition -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=1FF26142-6E1E-4E17-9DCD-994B339A69CF> Download the update

Non-Affected Software:
* Microsoft Windows 98, Microsoft Windows 98 Second Edition (SE), and
Microsoft Windows Millennium Edition (ME)

MSDTC Vulnerability:
A remote code execution and local elevation of privilege vulnerability
exists in the Microsoft Distributed Transaction Coordinator that could
allow an attacker who successfully exploited this vulnerability to take
complete control of the affected system.

CVE Information:
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-2119>
CAN-2005-2119

Mitigating Factors for MSDTC Vulnerability:
* Windows XP Service Pack 2 and Windows Server 2003 Service Pack 1
systems are not vulnerable to this issue.
* By default, on Windows Server 2003, the Microsoft Distributed
Transaction Coordinator is started, but it is not configured to support
Network DTC Access. An attacker must have valid logon credentials and be
able to log on locally to exploit this vulnerability. However, if an
administrator has enabled support for Network DTC Access, Windows Server
2003 systems could be vulnerable to remote code execution attacks by
anonymous users. For information about how to configure Network DTC
Access, visit the following Microsoft Web site.
* By default, on Windows XP Service Pack 1, the Microsoft Distributed
Transaction Coordinator is not started. This service must be running to
enable the remote attack vector. An attacker must have valid logon
credentials and be able to log on locally to exploit this vulnerability.
However, any local user can start this service unless the service has been
disabled by an administrator. As soon as this service is started, Windows
XP Service Pack 1 systems could be vulnerable to remote code execution
attacks by anonymous users. This is because on Windows XP Service Pack 1
systems, the Microsoft Distributed Transaction Coordinator service is
configured to allow Network DTC Access. For information about how to
configure Network DTC Access, visit the following Microsoft Web site.
* For customers who require the affected component, firewall best
practices and standard default firewall configurations can help protect
networks from attacks that originate outside the enterprise perimeter.
Best practices recommend that systems that are connected to the Internet
have a minimal number of ports exposed.

Workarounds for MSDTC Vulnerability:
Microsoft has tested the following workarounds. While these workarounds
will not correct the underlying vulnerability, they help block known
attack vectors. When a workaround reduces functionality, it is identified
in the following section.

* Disable the Distributed Transaction Coordinator
Disabling the Distributed Transaction Coordinator helps protect the
affected system from attempts to exploit this vulnerability. To disable
the Distributed Transaction Coordinator, follow these steps:

1. Click Start, and then click Control Panel. Alternatively, click Start,
point to Settings, and then click Control Panel.
2. Double-click Administrative Tools.
3. Double-click Component Services.
4. Click Services.
5. Double-click Distributed Transaction Coordinator.
6. In the Startup type list, click Disabled.
7. Click Stop, and then click OK.

You can also stop and disable the Distributed Transaction Coordinator by
using the following command at the command prompt:
sc stop MSDTC & sc config MSDTC start= disabled

Impact of Workaround: If you disable the Distributed Transaction
Coordinator, you cannot use any service or application that is dependant
on the Distributed Transaction Coordinator. This could include other
applications such as SQL Server, BizTalk Server, Exchange Server, or
Message Queuing. Also, this service is required in most clustering
configurations. Therefore, we recommend this workaround only on systems
that cannot install the security update.

* Use the Group Policy settings to disable the Distributed Transaction
Coordinator on all affected systems that do not require this feature.
Because the Distributed Transaction Coordinator is a possible attack
vector, disable it by using the Group Policy settings. You can disable the
startup of this service at the local, site, domain, or organizational unit
level by using Group Policy object functionality in Windows 2000 domain
environments or in Windows Server 2003 domain environments. For more
information about how to disable this service through logon scripts, see
Microsoft Knowledge Base Article <http://support.microsoft.com/kb/297789>
297789

Note You may also review the Windows 2000 Security Hardening Guide. This
guide includes information about how to disable services.

For more information about Group Policy, visit the following Web sites:
o
<http://www.microsoft.com/technet/prodtechnol/windowsserver2003/technologies/directory/activedirectory/stepbystep/gpfeat.mspx> Step-by-Step Guide to Understanding the Group Policy Feature Set
o
<http://www.microsoft.com/windows2000/techinfo/howitworks/management/grouppolwp.asp> Windows 2000 Group Policy
o
<http://www.microsoft.com/technet/prodtechnol/windowsserver2003/technologies/management/gp/default.mspx> Group Policy in Windows Server 2003

* Disable Network DTC Access
If you cannot install the security update, and you cannot disable the
Distributed Transaction Coordinator, you may want to disable Network DTC
Access. This option is only available on Windows XP and later operating
system versions. This still allows local transactions to complete, but it
helps protect from network based attacks that try to exploit this issue.
For information about how to configure Network DTC Access, visit the
following Microsoft Web site. To disable Network DTC Access, follow these
steps:

Warning Performing this procedure causes the affected service to start if
it was not started previously. Stop the MSDTC service on the MSDTC tab
before you close the configuration dialog boxes.

1. Click Start, and then click Control Panel. Alternatively, click Start,
point to Settings, and then click Control Panel.
2. Double-click Administrative Tools.
3. Double-Click Component Services, expand Component Services, expand
Computers, right-click My Computer and then click Properties,
4. Click the MSDTC tab, and then click Security Configuration.
5. In the Security Configuration dialog box, click to clear the Network
DTC Access check box.

Note This sets the following DWORD registry entry to 0 on non-clustering
environments. Clustering environments do not read the following registry
key. For Clustering environments, follow the steps that are listed in the
Disable the Distributed Transaction Coordinator bullet point.

HKLM\Software\Microsoft\MSDTC\Security\NetworkDtcAccess

Note You can also apply this setting to multiple systems by using Group
Policy. For more information about Group Policy, visit the following
Microsoft Web site.

6. Click OK, close the Component Services dialog box, and then close the
Administrative Tools dialog box.

Impact of Workaround: If you disable Network DTC Access, distributed
transaction could fail. This could impact other applications such as SQL
Server, BizTalk Server, or Message Queuing. Therefore, we recommend this
workaround only on systems that cannot install the security update.

* Block the following at the firewall:
o All unsolicited inbound traffic on ports greater than 1024
o Any other specifically configured RPC port

These ports can be used to initiate a connection with MSDTC. Blocking them
at the firewall will help protect systems that are behind that firewall
from attempts to exploit this vulnerability. Also, make sure that you
block any other specifically-configured RPC port on the remote system. We
recommend that you block all unsolicited inbound communication from the
Internet to help prevent attacks that may use other ports. While RPC can
use UDP ports 135, 137, 138, 445, and TCP ports 135, 139, 445, and 593,
the MSDTC service is not vulnerable over those ports.

Note Other protocols, such as Sequenced Packet Exchange (SPX) or NetBEUI,
could be used to communicate with the MSDTC service. If you are using
these protocols, you should block the appropriate ports for those
protocols. For more information about IPX and SPX, visit the following
Microsoft Web site.

* To help protect from network-based attempts to exploit this
vulnerability, use a personal firewall, such as the Internet Connection
Firewall, which is included with Windows XP and with Windows Server 2003.

By default, the Internet Connection Firewall feature in Windows XP and in
Windows Server 2003 helps protect your Internet connection by blocking
unsolicited incoming traffic. We recommend that you block all unsolicited
incoming communication from the Internet.

To enable the Internet Connection Firewall feature by using the Network
Setup Wizard, follow these steps:
1. Click Start, and then click Control Panel.
2. In the default Category View, click Network and Internet Connections,
and then click Setup or change your home or small office network. The
Internet Connection Firewall feature is enabled when you select a
configuration in the Network Setup Wizard that indicates that your system
is connected directly to the Internet.

To configure Internet Connection Firewall manually for a connection,
follow these steps:

1. Click Start, and then click Control Panel.
2. In the default Category View, click Networking and Internet
Connections, and then click Network Connections. (Windows Sever 2003
displays this as Network Connections)
3. Right-click the connection on which you want to enable Internet
Connection Firewall, and then click Properties.
4. Click the Advanced tab.
5. Under Windows Firewall, click Settings.
6. Click On, and then click OK.
7. Click the Exceptions tab. You may need to click Settings to display the
exceptions tab.
8. Verify that MSDTC.exe is not in the list of firewall exceptions, and
then click OK.

Note If you want to enable certain programs and services to communicate
through the firewall, click Settings on the Advanced tab, and then select
the programs, the protocols, and the services that are required.

* To help protect from network-based attempts to exploit this
vulnerability, enable advanced TCP/IP filtering on systems that support
this feature.
You can enable advanced TCP/IP filtering to block all unsolicited inbound
traffic. For more information about how to configure TCP/IP filtering, see
Microsoft Knowledge Base Article <http://support.microsoft.com/kb/309798>
309798.

* To help protect from network-based attempts to exploit this
vulnerability, block the affected ports by using IPsec on the affected
systems.
Use Internet Protocol security (IPsec) to help protect network
communications. Detailed information about IPsec and about how to apply
filters is available in Microsoft Knowledge Base Article
<http://support.microsoft.com/kb/313190> 313190 and Microsoft Knowledge
Base Article <http://support.microsoft.com/kb/813878> 813878. RPC uses a
broad range of ports, which may make it difficult to try to secure them
all by using IPsec. Microsoft Knowledge Base Article
<http://support.microsoft.com/kb/908472> 908472 documents how to restrict
RPC communication to a set of fixed ports and how to secure those ports by
using IPsec.

FAQ for MSDTC Vulnerability:
What is the scope of the vulnerability?
On Windows 2000 this is a remote code execution vulnerability. On Windows
XP Service Pack 1 and Windows Server 2003 this is a local privilege
elevation vulnerability. On Windows XP Service Pack 1, this also becomes a
remote code execution vulnerability if the Microsoft Distributed
Transaction Coordinator is started. An attacker who successfully exploited
this vulnerability could take complete control of an affected system. An
attacker could then install programs; view, change, or delete data; or
create new accounts with full user rights.

What causes the vulnerability?
An unchecked buffer in the Microsoft Distributed Transaction Coordinator.

What is the Microsoft Distributed Transaction Coordinator?
The Microsoft Distributed Transaction Coordinator (MSDTC) is a distributed
transaction facility for Microsoft Windows platforms. MSDTC uses proven
transaction processing technology. It is robust despite system failures,
process failures, and communication failures; it exploits loosely coupled
systems to provide scalable performance; and it is easy to install,
configure, and manage. The DTC service provides the following benefits:

* Reduces the cost of enterprise computing.
The DTC provides a sophisticated, low-cost distributed transaction
facility for users of networked, commodity-priced PCs and servers.

* Simplifies application development.
DTC transactions greatly simplify the application task of preserving
consistency, despite failures that can occur when updating application
data.

* Provides a consistent transaction model.
The DTC supports a variety of resource managers, including relational
databases, object-oriented databases, file systems, document storage
systems, and message queues.

* Enables software development using distributed software components.
The DTC provides a simple, object-oriented application programming
interface for initiating and controlling transactions.

For information about MSDTC, visit the following
<http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cossdk/html/39dad51b-4b40-4cca-925f-af812c749e8d.asp> Microsoft Web site.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could take
complete control of the affected system.

Who could exploit the vulnerability?
On Windows 2000, any anonymous user who could deliver a specially crafted
network message to the affected system could try to exploit this
vulnerability. On Windows XP Service Pack 1 and Windows Server 2003, an
attacker must be able to log on locally to a system and run a program to
try to exploit the vulnerability. Windows XP Service Pack 1 and Windows
Server 2003 are not vulnerable to remote anonymous attack in default
scenarios. User configuration is required on these operating system
versions in order to create the possibility of remote attack. If attacked
locally, an attacker could then run a specially-crafted application that
could exploit the vulnerability and gain complete control over the
affected system.

What systems are primarily at risk from the vulnerability?
Windows 2000 systems are primarily at risk from this vulnerability. On
Windows XP Service Pack 1 and Windows Server 2003, an attacker must have
valid logon credentials to exploit this vulnerability unless user
configuration has been performed that could allow remote anonymous
attacks. On Windows Server 2003, if an administrator has enabled support
for Network DTC Access, Windows Server 2003 systems could be vulnerable to
remote code execution attacks by anonymous users. For information about
how to configure Network DTC Access, visit the following Microsoft Web
site. Administrators can use the registry key that is documented at the
following Microsoft Web site to verify that Network DTC Access has not
been enabled.

Could the vulnerability be exploited over the Internet?
On Windows 2000 an attacker could try to exploit this vulnerability over
the Internet. Firewall best practices and standard default firewall
configurations can help protect against attacks that originate from the
Internet. Microsoft has provided information about how you can help
protect your PC. End users can visit the Protect Your PC Web site. IT
professionals can visit the Security Guidance Center Web site.

What does the update do?
The update removes the vulnerability by modifying the way that MSDTC
validates the length of a message before it passes the message to the
allocated buffer.

When this security bulletin was issued, had this vulnerability been
publicly disclosed?
No. Microsoft received information about this vulnerability through
responsible disclosure. Microsoft had not received any information to
indicate that this vulnerability had been publicly disclosed when this
security bulletin was originally issued.

When this security bulletin was issued, had Microsoft received any reports
that this vulnerability was being exploited?
No. Microsoft had not received any information to indicate that this
vulnerability had been publicly used to attack customers and had not seen
any examples of proof of concept code published when this security
bulletin was originally issued.

COM+ Vulnerability:
A remote code execution and local elevation of privilege vulnerability
exists in COM+ that could allow an attacker who successfully exploited
this vulnerability to take complete control of the affected system.

CVE Information:
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-1978>
CAN-2005-1978

Mitigating Factors for COM+ Vulnerability:
* On Windows XP Service Pack 2, on Windows Server 2003, and on Windows
Server 2003 Service Pack 1 an attacker must have valid logon credentials
and be able to log on locally to exploit this vulnerability. The
vulnerability could not be exploited remotely unless the attacker already
has administrative permissions.

* Firewall best practices and standard default firewall configurations
can help protect networks from attacks that originate outside the
enterprise perimeter. Best practices recommend that systems that are
connected to the Internet have a minimal number of ports exposed.

Workarounds for COM+ Vulnerability:
Microsoft has tested the following workarounds. While these workarounds
will not correct the underlying vulnerability, they help block known
attack vectors. When a workaround reduces functionality, it is identified
in the following section.

* Disable COM+
Disabling COM+ helps protect the affected system from attempts to exploit
this vulnerability. There are different ways to disable COM+, depending on
which platform you are using.

Important This bulletin contains information about how to modify the
registry. Make sure to back up the registry before you modify it. Make
sure that you know how to restore the registry if a problem occurs. For
more information about how to back up, restore, and modify the registry,
see Microsoft Knowledge Base Article 256986.

Warning Serious problems might occur if you modify the registry
incorrectly by using Registry Editor or by using another method. These
problems might require that you reinstall your operating system. Microsoft
cannot guarantee that these problems can be solved. Modify the registry at
your own risk.

* On Windows 2000, create a file that is named ~clbcatq.dll in the
%windir%\system32 folder. These steps create a similar environment as the
issue that is discussed in Microsoft Knowledge Based Article 246499. To
disable COM+ on Windows 2000, follow these steps:

1. Logon as an administrator.
2. Click Start, and then click Run and then type:

echo Workaround for KB902400 >%windir%\system32\~clbcatq.dll

3. Restart the system.
Note To re-enable COM+, delete the ~clbcatq.dll file and restart the
system.

* To disable COM+ on Windows XP and Windows Server 2003, create a
registry key and restart the computer to disable COM+:

On these operating system versions you can create a registry key and
restart the machine to disable COM+.

1. Click Start, click Run, type "regedt32" (without the quotation marks),
and then click OK.
2. In Registry Editor, locate the following registry key:

HKEY_LOCAL_MACHINE\Software\Microsoft\COM3

3. Double-click the COM+Enabled registry entry, and then change the value
to 0.

Note Make a note of the current value so that you can reverse this
procedure if required.

4. Quit Registry Editor and restart the system.

* Alternatively, you can paste the following text into a .reg file. Then,
double-click the .reg file while you are logged on locally as an
administrator:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\COM3]
"Com+Enabled"=dword:00000000

Note You can also apply this setting to multiple systems by using Group
Policy. For more information about Group Policy, visit the following
Microsoft Web Site.

Impact of Workaround: If you disable COM+, you cannot use any COM+
dependant applications. Customers should evaluate whether any
business-critical applications rely on COM+ services before they deploy
these workarounds. We recommend these workaround only on systems that
cannot install the security update. For information about COM+, visit the
following Microsoft Web site.

* Block the following at the firewall:
o UDP ports 135, 137, 138, and 445, and TCP ports 135, 139, 445, and 593
o If installed, COM Internet Services (CIS) or RPC over HTTP, which
listen on ports 80 and 443

These ports are used to initiate a connection with RPC. Blocking them at
the firewall will help protect systems that are behind that firewall from
attempts to exploit this vulnerability. Also, make sure that you block any
other specifically configured RPC port on the remote system. We recommend
that you block all unsolicited inbound communication from the Internet to
help prevent attacks that may use other ports. For more information about
ports that RPC uses, visit the following
<http://go.microsoft.com/fwlink/?LinkId=21312> Web site. For more
information about how to disable CIS, see Microsoft Knowledge Base Article
<http://support.microsoft.com/kb/825819> 825819.

* Disable DCOM
Disabling DCOM helps protect the affected system from remote attempts to
exploit this vulnerability. However, the affected system could still be
vulnerable to local elevation of privilege attacks that try to exploit
this vulnerability. For instructions on how to disable DCOM, see Microsoft
Knowledge Base Article <http://support.microsoft.com/kb/825750> 825750.

As an alternative to the steps that are documented In Microsoft Knowledge
Base Article <http://support.microsoft.com/kb/825750> 825750, alternately
you can paste the following text into a .reg file. Then, double-click the
reg file while you are logged on locally as an administrator:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Ole]
"EnableDCOM"="N"

Note You can also apply this setting to multiple systems by using Group
Policy. For more information about Group Policy, visit the following
Microsoft Web Site.

Impact of Workaround: If you disable DCOM, you cannot use any DCOM
dependant applications. Customers should evaluate whether any business
critical applications rely on DCOM services before you deploy this
workaround. There are potentially many built-in components and third-party
applications that are affected if you disable DCOM. We do not recommend
that you disable DCOM in your environment until you have tested to
discover what applications are affected. Disabling DCOM may not be
possible in all environments. Therefore, we recommend this workaround only
on systems that cannot install the security update. For information about
disabling DCOM, see Microsoft Knowledge Base Article
<http://support.microsoft.com/kb/825750> 825750.

FAQ for COM+ Vulnerability:
What is the scope of the vulnerability?
This is a remote code execution and local privilege elevation
vulnerability. On Windows 2000 and Windows XP Service Pack 1, an anonymous
attacker could remotely try to exploit this vulnerability. On Windows XP
Service Pack 2, Windows Server 2003, and Windows Server 2003 Service Pack
1, this is strictly a local privilege elevation vulnerability because only
an administrator can remotely access the affected component. An attacker
who successfully exploited this vulnerability could take complete control
of an affected system. An attacker could then install programs; view,
change, or delete data; or create new accounts with full user rights.

What causes the vulnerability?
The process that COM+ uses to create and use memory structures.

What is COM+?
COM+ is the next step in the evolution of the Microsoft Component Object
Model and Microsoft Transaction Server (MTS). COM+ handles resource
management tasks, such as thread allocation and security. It automatically
makes applications more scalable by providing thread pooling, object
pooling, and just-in-time object activation. COM+ also helps protect the
integrity of data by providing transaction support even if a transaction
spans multiple databases over a network. For information about COM+, visit
the following Microsoft Web site.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could take
complete control of the affected system.

Who could exploit the vulnerability?
On Windows 2000 and Windows XP Service Pack 1, an anonymous attacker could
try to exploit the vulnerability by creating a specially crafted network
message and sending the message to an affected system. The message could
then cause the affected system to execute code. On Windows XP Service Pack
2, Windows Server 2003 and Windows Server 2003 Service Pack 1, an attacker
must be able to log on locally to a system to try to exploit the
vulnerability. If an attacker logged on locally to a system, the attacker
could then run a specially crafted application to gain administrative
privileges to that system.

What systems are primarily at risk from the vulnerability?
Windows 2000 and Windows XP Service Pack 1 systems are primarily at risk
from this vulnerability. The vulnerability could not be exploited remotely
on Windows XP Service Pack 2, Windows Server 2003, and Windows Server 2003
Service Pack 1.

Could the vulnerability be exploited over the Internet?
Yes, by anonymous users on Windows 2000 and Windows XP Service Pack 1.
Firewall best practices and standard default firewall configurations can
help protect against attacks that originate from the Internet. Microsoft
has provided information about how you can help protect your PC. End users
can visit the Protect Your PC Web site. IT professionals can visit the
Security Guidance Center Web site.

On Windows XP Service Pack 2, Windows Server 2003, and Windows Server 2003
Service Pack 1, an attacker must be able to log on to the specific system
that is targeted for attack. An anonymous attacker cannot load and run a
program remotely by using this vulnerability on these operating system
versions.

What does the update do?
The update removes the vulnerability by modifying the way that COM+
creates and uses internal memory structures.

TIP Vulnerability:
A denial of service vulnerability exists that could allow an attacker to
send a specially crafted network message to an affected system. An
attacker could cause the Distributed Transaction Coordinator to stop
responding.

CVE Information:
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-1979>
CAN-2005-1979

Mitigating Factors for TIP Vulnerability:
* This is a denial of service vulnerability. This issue would not allow
an attacker to execute code or to elevate their user rights, but it could
cause the affected service to stop accepting requests.

* On Windows XP Service Pack 1, Windows XP Service Pack 2, Windows Server
2003, and Windows Server 2003 Service Pack 1, even if the Microsoft
Distributed Transaction Coordinator is started, the TIP protocol is not
enabled. An administrator must manually enable the TIP protocol for the
Distributed Transaction Coordinator to become vulnerable to this issue.

* If the Microsoft Distributed Transaction Coordinator stops responding
because of an attack, services that are not dependant on the Microsoft
Distributed Transaction Coordinator would continue to function normally.

* For customers who require the affected component, firewall best
practices and standard default firewall configurations can help protect
networks from attacks that originate outside the enterprise perimeter.
Best practices recommend that systems that are connected to the Internet
have a minimal number of ports exposed.

Workarounds for TIP Vulnerability:
Microsoft has tested the following workarounds. While these workarounds
will not correct the underlying vulnerability, they help block known
attack vectors. When a workaround reduces functionality, it is identified
in the following section.

You can also stop and disable the Distributed Transaction Coordinator by
using the following command at the command prompt:

sc stop MSDTC & sc config MSDTC start= disabled

Note You may also review the Windows 2000 Security Hardening Guide. This
guide includes information about how to disable services.

* Block TCP port 3372 at the firewall:

This port is used to initiate a connection with TIP. Blocking it at the
firewall will help protect systems that are behind that firewall from
attempts to exploit this vulnerability. Also, make sure that you block any
other specifically configured TIP ports on the remote system. We recommend
that you block all unsolicited inbound communication from the Internet to
help prevent attacks that may use other ports.

* To help protect from network-based attempts to exploit this
vulnerability, enable advanced TCP/IP filtering on systems that support
this feature.

You can enable advanced TCP/IP filtering to block all unsolicited inbound
traffic. For more information about how to configure TCP/IP filtering, see
Microsoft Knowledge Base Article <http://support.microsoft.com/kb/309798>
309798.

* To help protect from network-based attempts to exploit this
vulnerability, block the affected ports by using IPsec on the affected
systems.

Use Internet Protocol security (IPsec) to help protect network
communications. Detailed information about IPsec and about how to apply
filters is available in Microsoft Knowledge Base Article
<http://support.microsoft.com/kb/313190> 313190 and Microsoft Knowledge
Base Article <http://support.microsoft.com/kb/813878> 813878.

FAQ for TIP Vulnerability:
What is the scope of the vulnerability?
A denial of service vulnerability exists that could allow an attacker to
send a specially crafted network message to an affected system. An
attacker could cause the Distributed Transaction Coordinator to stop
responding. Note that the denial of service vulnerability would not allow
an attacker to execute code or to elevate their user rights, but it could
cause the affected system to stop accepting requests.

What causes the vulnerability?
The process that the Distributed Transaction Coordinator uses to validate
TIP requests.

* Reduces the cost of enterprise computing.
The DTC provides a sophisticated, low-cost distributed transaction
facility for users of networked, commodity-priced PCs and servers.

* Simplifies application development.
DTC transactions greatly simplify the application task of preserving
consistency, despite failures that can occur when updating application
data.

* Enables software development using distributed software components.
The DTC provides a simple, object-oriented application programming
interface for initiating and controlling transactions.

For information about MSDTC, visit the following Microsoft Web site.

What is TIP?
MSDTC supports Transaction Internet Protocol (TIP). TIP transactions
implicitly assume a two-pipe architecture. In this architecture, messages
that describe the work flow on one pipe, the application-to-application
pipe, and messages that control the transaction flow on another pipe, the
transaction manager-to-transaction manager pipe. MS DTC selects TIP when
an application program or resource manager explicitly uses the TIP COM
interfaces. MS DTC also uses TIP when TIP is the only communication
protocol that is common to both platforms. TIP is typically used when MS
DTC is used in conjunction with transaction managers from other companies.
For more information about TIP, visit the following Microsoft Web site.
TIP is an IETF standard, documented at the following IETF Web site. For
more information about security considerations that are associated with
TIP, visit the following Microsoft Web site.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could cause the
affected service to stop responding.

Who could exploit the vulnerability?
When the TIP protocol is available, any anonymous user who could deliver a
specially crafted network message to the affected system could try to
exploit this vulnerability.

How could an attacker exploit the vulnerability?
An attacker could try to exploit the vulnerability by creating a specially
crafted network message and sending the message to an affected system. The
message could then cause the affected service to stop responding.

What systems are primarily at risk from the vulnerability?
Windows 2000 based versions of the Microsoft Distributed Transaction
Coordinator are primarily at risk from this vulnerability because TIP is
enabled by default. If TIP is manually enabled on other operating system
versions, they would be equally vulnerable to this issue.

Could the vulnerability be exploited over the Internet?
Yes. An attacker could try to exploit this vulnerability over the
Internet. Firewall best practices and standard default firewall
configurations can help protect against attacks that originate from the
Internet. Microsoft has provided information about how you can help
protect your PC. End users can visit the Protect Your PC Web site. IT
professionals can visit the Security Guidance Center Web site.

What does the update do?
The update removes the vulnerability by modifying the way that MSDTC
validates TIP requests.

Distributed TIP Vulnerability:
A denial of service vulnerability exists that could allow an attacker to
send a specially crafted network message to an affected system. An
attacker could cause the Microsoft Distributed Transaction Coordinator
(MSDTC) to stop responding. This specially crafted message could also be
transferred through the affected system to another TIP server. This
distributed attack could cause the MSDTC on both systems to stop
responding.

CVE Information:
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-1980>
CAN-2005-1980

Mitigating Factors for Distributed TIP Vulnerability:
* This is a denial of service vulnerability. This issue would not allow
an attacker to execute code or to elevate their user rights, but it could
cause the affected services to stop accepting requests.

Workarounds for Distributed TIP Vulnerability:
Microsoft has tested the following workarounds. While these workarounds
will not correct the underlying vulnerability, they help block known
attack vectors. When a workaround reduces functionality, it is identified
in the following section.

You can also stop and disable the Distributed Transaction Coordinator by
using the following command at the command prompt:

sc stop MSDTC & sc config MSDTC start= disabled

Note You may also review the Windows 2000 Security Hardening Guide. This
guide includes information about how to disable services.

* Block TCP port 3372 at the firewall:

* To help protect from network-based attempts to exploit this
vulnerability, enable advanced TCP/IP filtering on systems that support
this feature.

* To help protect from network-based attempts to exploit this
vulnerability, block the affected ports by using IPsec on the affected
systems.

FAQ for Distributed TIP Vulnerability:
What is the scope of the vulnerability?
A denial of service vulnerability exists that could allow an attacker to
send a specially crafted network message to an affected system. An
attacker could cause the Distributed Transaction Coordinator to stop
responding. Note that the denial of service vulnerability would not allow
an attacker to execute code or to elevate their user rights, but it could
cause the affected system to stop accepting requests.

What causes the vulnerability?
The process that the Distributed Transaction Coordinator uses to validate
TIP requests.

* Reduces the cost of enterprise computing.
The DTC provides a sophisticated, low-cost distributed transaction
facility for users of networked, commodity-priced PCs and servers.

* Simplifies application development.
DTC transactions greatly simplify the application task of preserving
consistency, despite failures that can occur when updating application
data.

* Enables software development using distributed software components.
The DTC provides a simple, object-oriented application programming
interface for initiating and controlling transactions.

For information about MSDTC, visit the following Microsoft Web site.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could cause the
affected service to stop responding.

What does the update do?
The update removes the vulnerability by modifying the way that MSDTC
validates TIP requests.

ADDITIONAL INFORMATION

The information has been provided by Microsoft Product Security.
The original article can be found at:
<http://www.microsoft.com/technet/security/bulletin/MS05-051.mspx>
http://www.microsoft.com/technet/security/bulletin/MS05-051.mspx

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Wednesday, October 12, 2005

[NT] Vulnerabilities in MSDTC and COM+ Allows Remote Code Execution (MS05-051)

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