X.org X11 Server Attachments out-of-bounds write

Summaryinfo

A vulnerability, which was classified as critical, was found in X.org X11 Server. This impacts an unknown function of the component Attachments Handler. The manipulation results in out-of-bounds write. This vulnerability is identified as CVE-2026-50264. The attack is only possible with local access. There is not any exploit available.

Detailsinfo

A vulnerability was found in X.org X11 Server (affected version not known). It has been classified as critical. Affected is some unknown functionality of the component Attachments Handler. The manipulation with an unknown input leads to a out-of-bounds write vulnerability. CWE is classifying the issue as CWE-787. The product writes data past the end, or before the beginning, of the intended buffer. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

An out-of-bounds write flaw was found in the X.Org X server and Xwayland in DRIGetBuffers/DRIGetBuffersWithFormat. A client that requests multiple DRI2BufferBackLeft attachments and one DRI2BufferFrontLeft can trigger an out-of-bounds heap write. This may be used to crash the server, or for privilege escalation if the X server runs as root.

The advisory is shared for download at access.redhat.com. This vulnerability is traded as CVE-2026-50264 since 06/04/2026. The exploitability is told to be easy. The attack needs to be approached locally. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 06/06/2026).

The vulnerability scanner Nessus provides a plugin with the ID 318740 (Linux Distros Unpatched Vulnerability : CVE-2026-50264), which helps to determine the existence of the flaw in a target environment.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the databases at Tenable (318740) and CERT Bund (WID-SEC-2026-1774). Once again VulDB remains the best source for vulnerability data.

Affected

• Open Source X.Org X11
• Open Source Xwayland

Productinfo

Type

• Windowing System Software

Vendor

• X.org

Name

• X11 Server

License

• open-source

Website

• Vendor: https://www.x.org/

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Once again VulDB remains the best source for vulnerability data.

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