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iDefense Security Advisory 06.11.08
http://labs.idefense.com/intelligence/vulnerabilities/ Jun 11, 2008
I. BACKGROUND The X Window System is a graphical windowing system based on a client/server model. For more information, see the vendor's site found at the following link.
II. DESCRIPTION Local exploitation of multiple memory corruption vulnerabilities in the X.Org X server, as included in various vendors' operating system distributions, could allow an attacker to execute arbitrary code with the privileges of the X server, typically root.
Multiple vulnerabilities are present in the Record and Security extensions. In both cases, untrusted values are taken from a client request, and used to swap the byte order of heap memory that follows the client request. Since the number of bytes to swap is not properly validated, it is possible to corrupt heap memory located after the request. The following functions contain vulnerable code:
III. ANALYSIS Exploitation allows an attacker to execute arbitrary code with the privileges of the X server, typically root. In order to exploit these vulnerabilities, an attacker must be able to send commands to an affected X server. This typically requires access to the console or access to the same account as a user who is on the console. One method of gaining the required access is to remotely exploit a vulnerability in, for example, a graphical web browser. This would then allow an attacker to exploit this vulnerability and elevate their privileges to root.
If an X Server is configured to listen for TCP based client connections, and a client is granted access to create sessions (via the xhosts file), then these vulnerabilities can be exploited remotely.
IV. DETECTION iDefense has confirmed the existence of these vulnerabilities in X server 1.4 included with X.org X11R7.3, with all patches as of 03/01/08 applied. Previous versions may also be affected.
V. WORKAROUND Access to the vulnerable code in the SECURITY extension can be prevented by preventing the X server from loading the extension. However, doing so may seriously impair the functionality of the server. Adding the following lines to the X configuration file will disable the SECURITY extension:
Option "SECURITY" "disable"
VI. VENDOR RESPONSE The X.Org team has addressed these vulnerabilities by releasing patches for version 1.4 of the X server. For more information, consult the X.Org advisory at the following URL.
VII. CVE INFORMATION The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2008-1377 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 03/26/2008 Initial vendor notification 03/26/2008 Initial vendor response 06/11/2008 Coordinated public disclosure
IX. CREDIT This vulnerability was reported to iDefense by regenrecht.
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