Permissions, Privileges, and Access Controls
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.
CWE-264 - Permissions Privileges and Access Controls
CWE 264 (permissions, privileges, and access controls) is not a weakness in and of itself, rather it is a category of weaknesses related to the management of permissions, privileges, and other security features used to perform access control. If not addressed, the weaknesses in this category allow attackers to gain privileges for an unintended sphere of control, access sensitive information, and execute arbitrary commands.