PatchSiren

PatchSiren cyber security CVE debrief

CVE-2026-50256 Red Hat CVE debrief

A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. A mismatch between the X server and the libXfont2 library's maximum font name length can cause a stack buffer overflow during font alias resolution. The server allocates a 256 byte stack buffer but libXfont2's alias target name length is 1024 bytes. A font alias name between 257 and 1023 bytes causes the X server to copy that name into the undersized stack buffer without further checks. 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 prevent potential crashes or privilege escalation.

Technical summary

The X.Org X server and Xwayland are vulnerable to a stack-based buffer overflow (CWE-121) due to a mismatch in font name length handling. The X server allocates a 256-byte stack buffer for font alias resolution, but libXfont2 allows alias target names up to 1024 bytes. A specially crafted font alias name between 257 and 1023 bytes can cause a buffer overflow.

Defensive priority

high

Recommended defensive actions

  • Apply patches or updates from vendors like Red Hat to address the vulnerability.
  • Restrict access to the X server to prevent potential exploitation.
  • Monitor for suspicious activity or anomalies in X server logs.

Evidence notes

The CVE-2026-50256 record was published on 2026-06-05T12:16:38.727Z and last modified on 2026-06-08T16:45:14.903Z. The vulnerability affects X.Org X server and Xwayland, with CVSS score of 7.8 and HIGH severity.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-50256 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-50256

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

  • CVE-2026-50256 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-50256

    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.