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CVE-2026-50259 Red Hat CVE debrief

CVE-2026-50259 is a HIGH severity vulnerability in X.Org X server and Xwayland. A stack-based buffer overflow flaw was found in _XkbSetMapChecks(), which declares a fixed-size stack buffer mapWidths[256] indexed by key type index. The helper function CheckKeyTypes() writes to this buffer at a client-controlled offset, allowing a stack buffer overflow. This may be used to crash the server, or for privilege escalation if the X server runs as root.

Vendor
Red Hat
Product
Red Hat Enterprise Linux 10
CVSS
HIGH 7.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-05
Original CVE updated
2026-08-05
Advisory published
2026-06-05
Advisory updated
2026-08-05

Who should care

Users of X.Org X server and Xwayland should be aware of this vulnerability, especially if the X server runs as root.

Technical summary

The vulnerability exists in the X.Org X server and Xwayland. The _XkbSetMapChecks() function declares a fixed-size stack buffer mapWidths[256] indexed by key type index. The CheckKeyTypes() helper function writes to this buffer at a client-controlled offset, allowing a stack buffer overflow.

Defensive priority

HIGH

Recommended defensive actions

  • Apply patches or updates provided by the vendor.
  • Restrict access to the X server.
  • Monitor for suspicious activity.

Evidence notes

The CVE-2026-50259 vulnerability was found in the X.Org X server and Xwayland. The vulnerability has a CVSS score of 7.8 and is classified as HIGH severity.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-50259 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-50259

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-50259 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-50259

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.