Untrusted search path vulnerability in pam_motd (aka the MOTD module) in libpam-modules before 1.1.3-2ubuntu2.1 on Ubuntu 11.10, before 1.1.2-2ubuntu8.4 on Ubuntu 11.04, before 1.1.1-4ubuntu2.4 on Ubuntu 10.10, before 1.1.1-2ubuntu5.4 on Ubuntu 10.04 LTS, and before 0.99.7.1-5ubuntu6.5 on Ubuntu 8.04 LTS, when using certain configurations such as "session optional pam_motd.so", allows local users to gain privileges by modifying the PATH environment variable to reference a malicious command, as demonstrated via uname.