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vulnerability bulletin CVE-2006-5397

libX11: descriptor leak

Synthesis of the vulnerability

A file descriptor is unnecessarily opened in libX11, but permits an attacker to access a file.
Impacted products: Mandriva Linux, XOrg Bundle ~ not comprehensive, libX11.
Severity of this bulletin: 2/4.
Consequences of an intrusion: data reading.
Hacker's origin: user shell.
Creation date: 02/11/2006.
Références of this threat: 8699, BID-20845, CVE-2006-5397, MDKSA-2006:199, VIGILANCE-VUL-6273.

Description of the vulnerability

The modules/im/ximcp/imLcIm.c file of libX11 manages input methods (generally used for Asian characters).

The XCOMPOSEFILE environment variable indicates the name of a file defining how to compose characters, by pressing several keys.

The file indicated by this variable is incorrectly opened twice in the XimCreateDefaultTree() function of imLcIm.c. The first file descriptor is never closed.

A local attacker can thus set XCOMPOSEFILE, then run a suid/sgid program linked with libX11 (such as xterm), in order to open the file, then to access its descriptor. The attacker can thus read its content.
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