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 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.