Debian Security Advisory DSA 870-1 – Tavis Ormandy noticed that sudo, a program that provides limited super user privileges to specific users, does not clean the environment sufficiently. The SHELLOPTS and PS4 variables are dangerous and are still passed through to the program running as privileged user. This can result in the execution of arbitrary commands as privileged user when a bash script is executed. These vulnerabilities can only be exploited by users who have been granted limited super user privileges.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/40986/dsa-870-1.txt
Source: https://packetstormsecurity.com/files/40986/Debian-Linux-Security-Advisory-870-1.html