Debian glibc 2 Symlink Vulnerability

Glibc 2 is the latest version of the GNU C Library. is used to load shared libraries for dynamically-linked programs on Unix systems. The version of from glibc2 fails to clear environment variables LD_DEBUG_OUTPUT and LD_DEBUG when running suid programs.

These two variables cause a program to create debug files in the directory specified by LD_DEBUG_OUTPUT. These files have predictable filenames, composed of the word DEBUG and the process ID. When writes to these debug files, it will follow symbolic links. As a result, it is possible for an attacker to anticipate a 'debug' filename and, in a path to which the attacker has write privileges, create a symbolic link pointing to a target file . The attacker can then specify this path as LD_DEBUG_OUTPUT, set the LD_DEBUG variable, and run the target suid program. If the 'debug' filename was correctly guessed, the suid program will overwrite whatever is pointed to by the symlink.


Privacy Statement
Copyright 2010, SecurityFocus