I. 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/
II. 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.
III. 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.
IV. DETECTION
iDefense confirmed the existence of this vulnerability in rdesktop
version 1.5.0. Previous versions may also be affected.
V. WORKAROUND
iDefense is currently unaware of any effective workaround for this
issue.
VI. 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
VII. 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.
VIII. DISCLOSURE TIMELINE
11/12/2007 Initial vendor notification
11/19/2007 Initial vendor response
05/07/2008 Public disclosure
IX. CREDIT
The discoverer of this vulnerability wishes to remain anonymous.
Get paid for vulnerability research
http://labs.idefense.com/methodology/vulnerability/vcp.php
Free tools, research and upcoming events
http://labs.idefense.com/
X. LEGAL NOTICES
Copyright © 2008 iDefense, Inc.
Permission is granted for the redistribution of this alert electronically. It may not be edited in
any way without the express written consent of iDefense. If you wish to reprint the whole or any
part of this alert in any other medium other than electronically, please e-mail customer service for
permission.
Disclaimer: The information in the advisory is believed to be accurate at the time of publishing
based on currently available information. Use of the information constitutes acceptance for use in
an AS IS condition. There are no warranties with regard to this information. Neither the author nor
the publisher accepts any liability for any direct, indirect, or consequential loss or damage
arising from use of, or reliance on, this information.
