(1) bash before 1.14.7, and (2) tcsh 6.05 allow local users to gain privileges via directory names that contain shell metacharacters ( back-tick), which can cause the commands enclosed in the directory name to be executed when the shell expands filenames using the \w option in the PS1 variable.

The prompt parsing in bash allows a local user to execute commands as another user by creating a directory with the name of the command to execute.

A vulnerability was found in popd. It can be tricked to free a user supplied address in the following way:

$ popd +-111111

This could be used to bypass restricted shells (rsh) on some environments to cause use-after-free.

References:

http://seclists.org/oss-sec/2016/q4/445

Stack-based buffer overflow in lib/sh/eaccess.c in GNU Bash before 4.2 patch 33 might allow local users to bypass intended restricted shell access via a long filename in /dev/fd, which is not properly handled when expanding the /dev/fd prefix.

A vulnerability was found in a way bash expands the $HOSTNAME. Injecting the hostname with malicious code would cause it to run each time bash expanded \h in the prompt string.

References:

http://seclists.org/oss-sec/2016/q3/528

Ubuntu bug:

https://bugs.launchpad.net/ubuntu/+source/bash/+bug/1507025