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CVE-2026-50261 Red Hat CVE debrief

CVE-2026-50261 is a HIGH severity vulnerability in X.Org X server and Xwayland. A use-after-free flaw was found in SyncChangeCounter(). A client that sets up multiple SyncCounters can trigger a use-after-free when destroying those counters via a second client connection while changing those counters. 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 apply patches or mitigations to address this vulnerability.

Technical summary

The vulnerability has a CVSS score of 7.8 and is classified as HIGH severity. The vulnerability is caused by a use-after-free flaw in SyncChangeCounter().

Defensive priority

HIGH

Recommended defensive actions

  • Apply patches or updates from the vendor as soon as possible.
  • Restrict access to the X server to trusted users only.
  • Monitor for suspicious activity on the X server.

Evidence notes

The CVE record was published on 2026-06-05T12:16:39.617Z and modified on 2026-06-05T13:27:38.750Z.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-50261 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-50261

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

  • CVE-2026-50261 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-50261

    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.