Public Vulnerability Reports

Multiple Vendor rdesktop process_redirect_pdu() BSS Overflow Vulnerability

07.05.08

BACKGROUND

rdesktop is an open source client that speaks the Remote Desktop Protocol (RDP). This allows Unix-based users to login to Windows Terminal Servers. More information is available at the following URL.

http://www.rdesktop.org/

DESCRIPTION

Remote exploitation of a BSS overflow vulnerability in rdesktop, as included in various vendors' operating system distributions, allows attackers to execute arbitrary code with the privileges of the logged-in user.

The vulnerability exists within the code responsible for reading in an RDP redirect request. This request is used to redirect an RDP connection from one server to another. When parsing the redirect request, the rdesktop client reads several 32-bit integers from the request packet. These integers are then used to control the number of bytes read into statically allocated buffers. This results in several buffers located in the BSS section being overflowed, which can lead to the execution of arbitrary code.

ANALYSIS

Exploitation of this vulnerability results in the execution of arbitrary code with the privileges of the logged in user. In order to exploit this vulnerability, an attacker must persuade a targeted user to connect to a malicious RDP server.

DETECTION

iDefense confirmed the existence of this vulnerability in rdesktop version 1.5.0. Previous versions may also be affected.

WORKAROUND

iDefense is currently unaware of any effective workaround for this issue.

VENDOR RESPONSE

The rdesktop maintainer has addressed this vulnerability with CVS revision 1.102 of rdp.c. For more information, visit the following URL.

http://rdesktop.cvs.sourceforge.net/rdesktop/rdesktop/rdp.c?annotate=1.102&pathrev=HEAD#l1337

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2008-1802 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org/), which standardizes names for security problems.

DISCLOSURE TIMELINE

11/12/2007 Initial vendor notification
11/19/2007 Initial vendor response
05/07/2008 Public disclosure

CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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LEGAL NOTICES

Copyright © 2008 Verisign, Inc.

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