iDefense Security Advisory 05.07.08 http://labs.idefense.com/intelligence/vulnerabilities/ May 07, 2008 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 an integer underflow 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 request. When reading a request, a 16-bit integer value that represents the number of bytes that follow is taken from the packet. This value is then decremented by 4, and used to calculate how many bytes to read into a heap buffer. The subtraction operation can underflow, which will then lead to the heap buffer being overflowed. 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 1.20 of iso.c. For more information, visit the following URL. http://rdesktop.cvs.sourceforge.net/rdesktop/rdesktop/iso.c?annotate=1.20&diff_format=h&pathrev=HEAD#l101 VII. CVE INFORMATION The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2008-1801 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 customerservice@xxxxxxxxxxxx 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.
