CVE-2026-50258: redhat enterprise_linux Stack-based Buffer Overflow

Vulnerability summary

CVE-2026-50258 is a high (CVSS 7.8) Stack-based Buffer Overflow vulnerability in redhat enterprise_linux. EPSS estimates a 0.22% chance of exploitation in the next 30 days, higher than 11.8% of scored vulnerabilities.

Timeline

1. 05-06-2026
   PublishedVulnerability first disclosed.
2. 28-09-2026
   Last modifiedVulnerability information updated.

Description

A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. The X server has multiple stack buffers sized XkbMaxShiftLevel * XkbNumKbdGroups but CheckKeyTypes() does not verify or clamp non-canonical key types to XkbMaxShiftLevel. A client can change key types to excessive shift levels and trigger stack overflows. This is caused by an incomplete fix of CVE-2025-26597. This may be used to crash the server, or for privilege escalation if the X server runs as root.

• CWE-121Stack-based Buffer OverflowA stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).