The rxvt-unicode package is vulnerable to a remote code execution, in the Perl background extension, when an attacker can control the data written to the user's terminal and certain options are set.

rxvt-unicode 9.22, rxvt 2.7.10, mrxvt 0.5.4, and Eterm 0.9.7 allow (potentially remote) code execution because of improper handling of certain escape sequences (ESC G Q). A response is terminated by a newline.

rxvt 2.6.4 opens a terminal window on :0 if the DISPLAY environment variable is not set, which might allow local users to hijack X11 connections. NOTE: it was later reported that rxvt-unicode, mrxvt, aterm, multi-aterm, and wterm are also affected. NOTE: realistic attack scenarios require that the victim enters a command on the wrong machine.

rxvt-unicode before 6.3, on certain platforms that use openpty and non-Unix pty devices such as Linux and most BSD platforms, does not maintain the intended permissions of tty devices, which allows local users to gain read and write access to the devices.