A crash was reported in xterm prior to patch #366 when processing a specially crafted sequence of combining characters. The cause is an out of bounds write, which may be exploitable to cause arbitrary code execution.

https://www.openwall.com/lists/oss-security/2021/02/09/7 https://invisible-island.net/xterm/xterm.log.html

xterm before 375 allows code execution via font ops, e.g., because an OSC 50 response may have Ctrl-g and therefore lead to command execution within the vi line-editing mode of Zsh. NOTE: font ops are not allowed in the xterm default configurations of some Linux distributions.

xterm before 380 supports ReGIS reporting for character-set names even if they have unexpected characters (i.e., neither alphanumeric nor underscore), aka a pointer/overflow issue. This can only occur for xterm installations that are configured at compile time to use a certain experimental feature.

The default configuration of xterm on Debian GNU/Linux sid and possibly Ubuntu enables the allowWindowOps resource, which allows user-assisted attackers to execute arbitrary code or have unspecified other impact via escape sequences.

xterm through Patch 370, when Sixel support is enabled, allows attackers to trigger a buffer overflow in setsixel in graphicssixel.c via crafted text.