CVE-2026-33999 Xorg: xwayland: x.org x server: denial of service via integer underflow in xkb compatibility map handling
An attacker with X11 access can trigger a buffer read overrun via integer underflow in XKB handling, causing denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-33999?
CVE-2026-33999 is a high-severity vulnerability in Red Hat Enterprise Linux 10, published on 23 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Weakness: CWE-191
Which versions are affected by CVE-2026-33999?
How do I fix CVE-2026-33999?
Apply the vendor's patch.
Is CVE-2026-33999 being exploited?
There is no known exploitation of CVE-2026-33999 in the wild and no public exploit code.
Sources
Also known as AZL-84630, AZL-84839, BELL-CVE-2026-33999, DEBIAN-CVE-2026-33999, ECHO-3bf6-384c-577f, GHSA-g562-3mh5-27v6 and 1 more.