CVE-2026-33999

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.

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.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

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.