The vulnerability CVE-2026-50258 affects the X.Org X server and Xwayland in Red Hat Enterprise Linux 10. It is a stack-based buffer overflow caused by the CheckKeyTypes() function failing to verify or clamp non-canonical key types to the maximum allowed shift level (XkbMaxShiftLevel). This allows a client to set key types with excessive shift levels, leading to stack overflow conditions. The issue stems from an incomplete fix of CVE-2025-26597. The flaw can be exploited to crash the X server or escalate privileges if the server runs as root. Red Hat has issued security advisories (RHSA-2026:26562 and RHSA-2026:26566) that include patches for this vulnerability along with multiple other related security fixes in the xorg-x11-server and Xwayland components. The CVSS v3.1 base score is 7.8, indicating high severity, with impact on confidentiality, integrity, and availability. The affected versions include Red Hat Enterprise Linux 10 from 10.0.0 up to but not including 10.2.2.

Successful exploitation of this vulnerability can cause a stack-based buffer overflow in the X.Org X server or Xwayland, potentially leading to denial of service (server crash) or privilege escalation if the X server is running with root privileges. The CVSS score of 7.8 reflects high impact on confidentiality, integrity, and availability. No known exploits in the wild have been reported at this time.

Red Hat has released official security updates that fix this vulnerability in the xorg-x11-server and xorg-x11-server-Xwayland packages for Red Hat Enterprise Linux 10. Users should apply the updates as described in Red Hat advisories RHSA-2026:26562 and RHSA-2026:26566. The advisories provide detailed instructions and updated package versions. Applying these patches fully mitigates the vulnerability. No additional mitigation steps are required beyond applying the official fixes.