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Rapid7 Advisory R7-0013: Heap Corruption in Gaim-Encryption Plugin

CVE: CAN-2003-0163
Bugtraq ID: 7182


Summary

April 11, 2003 - GAIM is a multi-protocol instant messaging client that is compatible with AIM, ICQ, MSN Messenger, Jabber, and other protocols. The Gaim-Encryption plugin provides transparent message encryption between two users.

The Gaim-Encryption plugin does insufficient validation on the message length parameter supplied by a remote user. This allows an arbitrary heap location to be overwritten with a zero byte and will also cause an unbounded read into the heap.

The most obvious impact of this vulnerability would be a denial of service to the GAIM client. While this vulnerability is not likely to be exploitable, exploitation cannot be ruled out.

Please note that Gaim-Encryption is not part of GAIM and is not developed by GAIM.

Affected system(s):

KNOWN VULNERABLE:

  • gaim-encryption 1.15 and earlier

NOT VULNERABLE:

  • gaim-encryption 1.16 and later

Vendor Info

William Tompkins
http://gaim-encryption.sourceforge.net/

The author was notified and a fixed version was released on March 16th, 2003.

Detailed Analysis

The decrypt_msg function is responsible for decrypting encrypted GAIM messages. It reads the message length from a user-supplied header using sscanf. While some bounds checking is performed, a negative length is not properly handled. This causes the NUL termination of the message string to place a zero byte in an arbitrary location in memory rather than at the end of the string where it belongs.

Solution

Upgrade to version 1.16 of the Gaim-Encryption plugin. Note that while a patched version of 1.15 was released, some versions of 1.15 may still be vulnerable.

Disclaimer & Copyright

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This advisory Copyright (C) 2003 Rapid7, LLC. Permission is hereby granted to redistribute this advisory, providing that no changes are made and that the copyright notices and disclaimers remain intact.