iDefense Security Advisory 01.17.08
http://labs.idefense.com/intelligence/vulnerabilities/ 
Jan 17, 2008

I. BACKGROUND

The X Window System (or X11) is a graphical windowing system used on
Unix-like systems. It is based on a client/server model. More
information about about The X Window system is available at the
following URL.

http://en.wikipedia.org/wiki/X_Window_System 

II. DESCRIPTION

Local exploitation of multiple memory corruption vulnerabilities in the
X.Org X server, as included in various vendors' operating system
distributions, allows attackers to execute arbitrary code with the
privileges of the X server, typically root.

Vulnerable code exists within multiple functions in the XInput
extension. By sending specially crafted X11 requests, an attacker is
able to corrupt heap memory located after their request data. This
results in a potentially exploitable condition.

III. ANALYSIS

Exploitation allows an attacker to execute arbitrary code with root
privileges. 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.

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.Org
X11 version R7.3. Previous versions may also be affected.

V. WORKAROUND

iDefense is currently unaware of any workarounds for this issue. The
XInput extension is normally compiled into the X Server; as such, it's
not possible to disable it from being loaded in the configuration file.

VI. VENDOR RESPONSE

The X.Org team has addressed these vulnerabilities with the release of
Xserver version 1.4.1. Additionally, patches for versions 1.4 and 1.2
have been made available. For more information, consult the X.Org
advisory at the following URL.

http://lists.freedesktop.org/archives/xorg/2008-January/031918.html 

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2007-6427 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

11/29/2007  Initial vendor notification
12/04/2007  Initial vendor response
01/17/2008  Coordinated public disclosure

IX. CREDIT

These vulnerabilities were reported to VeriSign iDefense by regenrecht.

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X. LEGAL NOTICES

Copyright =A9 2008 iDefense, Inc.

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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
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