[UNIX] Multiple Vendor X Font Server Multiple Vulnerabilities

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Multiple Vendor X Font Server Multiple Vulnerabilities
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SUMMARY

The <http://en.wikipedia.org/wiki/X_Window_System> X Window System (or
<http://www.x.org/wiki/> X11) is a graphical windowing system used on
Unix-like systems. It is based on a client/server model. The X Window
System font server (xfs) is used to render fonts for the X server.

Remote exploitation of a multiple vulnerabilities in X.Org Foundation's X
Font Server, as included in various vendors' operating system
distributions, could allow an attacker to execute arbitrary code.

DETAILS

Vulnerable Systems:
* XFS version X11R7.2-1.0.4 (Previous versions may also be affected)

An integer overflow vulnerability exists within the handlers for the
QueryXBitmaps and QueryXExtents protocol requests. Both requests result in
a call to the build_range() function. This function takes a 32bit integer
from the request, and uses it in an arithmetic operation that calculates
the size of a dynamic buffer. This calculation can overflow, which leads
to an improperly sized memory allocation. This results in a heap overflow.

Additionally, a heap corruption vulnerability exists within the handlers
for the QueryXBitmaps and QueryXExtents protocol requests. Both requests
result in a call to the swap_char2b() function. This function takes a
32bit integer from the request, and uses it as the number of bytes to swap
in the request buffer. This allows an attacker to swap an arbitrary number
of bytes on the heap.

Exploitation of these vulnerabilities could result in the execution of
arbitrary code with the privileges of the X Font Server, usually 'xfs'.

On current versions of Solaris, these vulnerabilities are remotely
exploitable. The XFS service is turned on by default, and listens on TCP
port 7100. On modern Linux systems, these vulnerabilities are only locally
exploitable since the server is configured to listen on a UNIX socket
only.

Workaround:
On Solaris, stop XFS from listening remotely by disabling it via the
service manager.

Vendor Status:
The X.Org team has addressed these vulnerabilities with the release of XFS
version 1.0.5. Additionally, a patch for version 1.0.4 has been made
available. For more information, consult the X.Org advisory at the
following URL:

<http://lists.freedesktop.org/archives/xorg-announce/2007-October/000416.html> http://lists.freedesktop.org/archives/xorg-announce/2007-October/000416.html

CVE Information:
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-4568>
CVE-2007-4568

Disclosure Timeline:
* 09/05/2007 - Initial vendor notification
* 09/08/2007 - Initial vendor response
* 10/02/2007 - Coordinated public disclosure

ADDITIONAL INFORMATION

The information has been provided by iDefense.
The original article can be found at:

<http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=602>

http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=602

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