CVE-2026-33999

DOCUMENTATION: A flaw was found in the X.Org X server. This integer underflow vulnerability, specifically in the XKB compatibility map handling, allows an attacker with local or remote X11 server access to trigger a buffer read overrun. This can lead to memory-safety violations and potentially a denial of service (DoS) or other severe impacts. 

            STATEMENT: An Important integer underflow vulnerability exists in the X.Org X server's XKB compatibility map handling. This flaw allows an attacker with local or remote X11 server access to trigger a buffer read overrun, leading to memory-safety violations and potential denial of service. Red Hat Enterprise Linux systems utilizing the X.Org X server in graphical environments are affected.

            MITIGATION: To mitigate this issue, restrict access to the X11 server. For remote access, disable X11 forwarding in SSH configurations if not required. Edit /etc/ssh/sshd_config and set X11Forwarding no. After modifying the configuration, restart the sshd service using systemctl restart sshd. Disabling X11 forwarding may impact remote graphical applications.