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X.Org X11 User Privilege Checking Security Bypass
Secunia Advisory: SA19307
Release Date: 2006-03-21
Last Update: 2006-08-17
Popularity: 10,083 views

Critical:
Less critical
Impact: Security Bypass
Where: Local system
Solution Status: Vendor Patch

Software:X Window System 11 (X11) 6.x
X Window System 11 (X11) 7.x

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CVE reference:CVE-2006-0745


Description:
A vulnerability has been reported in X11, which can be exploited by malicious, local users to bypass certain security restrictions.

Normally, a non-root user is not allowed to pass arguments to the "-logfile" and "-modulepath" command line options. However, an error exists when checking a user's privileges as the address of the "geteuid()" function is tested and not the result of the function. This can be exploited to pass arbitrary arguments to the "-logfile" and "-modulepath" options, which allows overwriting of arbitrary files or execution of arbitrary code with root privileges.

The vulnerability has been reported in X.Org server 1.0.0 (as shipped with X11R7.0) and later, X11R6.9.0 and X11R7.0 (including all release candidates). X11R6.8.2 and prior versions are reportedly not affected.

Solution:
-- X.Org Server (X11R7) --
Apply patch for versions 1.0.0 and 1.0.1 or update to version 1.0.2.

Patches:
http://xorg.freedesktop.org/releases/...atches/xorg-server-1.0.1-geteuid.diff
80db6a3ab76334061ec6102e74ef5607
http://xorg.freedesktop.org/releases/...atches/xorg-server-1.0.1-geteuid.diff
44b44fa3efc63697eefadc7c2a1bfa50a35eec91

-- X.Org Server (X11R6.9) --

Apply patch:
http://xorg.freedesktop.org/releases/X11R6.9.0/patches/x11r6.9.0-geteuid.diff
de85e59b8906f76a52ec9162ec6c0b63
http://xorg.freedesktop.org/releases/X11R6.9.0/patches/x11r6.9.0-geteuid.diff
f9b73b7c1bd7d6d6db6d23741d5d1125eea5f860

Provided and/or discovered by:
Discovered with Coverity Prevent code audit tool and reported by vendor.

Changelog:
2006-08-17: Added link to US-CERT.

Original Advisory:
http://lists.freedesktop.org/archives/xorg/2006-March/013992.html

Other References:
US-CERT VU#837857:
http://www.kb.cert.org/vuls/id/837857


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