CVE-2026-50259

A stack-based buffer overflow in the X.Org X server and Xwayland is triggered by an unchecked key mapping request that writes past the bounds of a fixed 256‑element array. This flaw allows an attacker controlling the client request to overwrite local stack memory, potentially corrupting execution or enabling arbitrary code execution. If the X server runs with root privileges, the overflow can be used for privilege escalation; otherwise it typically results in a crash. The vulnerability is classified as CWE‑121.

Red Hat Enterprise Linux releases 6 through 10 are affected because the xorg‑x11‑server and xorg‑x11‑server‑xwayland packages bundled with those distributions contain the unpatched code. Any system that runs either of those packages without the latest patch is susceptible, regardless of minor version.

The CVSS score of 7.8 indicates high severity, while the EPSS score is not available and the issue is not listed in the CISA KEV catalog. An attacker can trigger the failure by sending a malicious client request; local users who can talk to the X server, or remote users if the server accepts network connections, can exploit it. Successful exploitation allows an attacker to crash the server, and if the server runs as root, the overflow can be leveraged to execute code with root privileges, achieving privilege escalation. Administrators should treat this as a critical patching priority.