rxvt-unicode before 9.20 does not properly handle OSC escape sequences, which allows user-assisted remote attackers to manipulate arbitrary X window properties and execute arbitrary commands.

RXVT-Unicode 3.4 and 3.5 does not properly close file descriptors, which allows local users to access the terminals of other users and possibly gain privileges.

Buffer overflow in command.C for rxvt-unicode before 5.3 allows remote attackers to execute arbitrary code via a crafted file containing long escape sequences.