glibc2 does not properly clear the LD_DEBUG_OUTPUT and LD_DEBUG environmental variables when a program is spawned from a setuid program, which could allow local users to overwrite files via a symlink attack.

The unsetenv function in glibc 2.1.1 does not properly unset an environmental variable if the variable is provided twice to a program, which could allow local users to execute arbitrary commands in setuid programs by specifying their own duplicate environmental variables such as LD_PRELOAD or LD_LIBRARY_PATH.

The resolver in glibc 2.1.3 uses predictable IDs, which allows a local attacker to spoof DNS query results.