# CVE-2026-94286: libXtst out-of-bounds read in RECORD reply parser

Source: https://junglewise.ai/threats/cve-2026-94286-an-out-of-bounds-read-in-libxtst-s-record-reply-parser-in-libxtst  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-28. Updated: 2026-09-28  
License: CC BY 4.0 with a link back

CVE-2026-94286 · Severity: high · CVSS 7.1 · Published 2026-09-28

libXtst is an X Window System client library that handles input device recording. A malicious X server can send crafted RECORD replies that cause an out-of-bounds memory read in libXtst before version 1.2.6, crashing X client applications that rely on this library for event interception and recording.

Vendors: [Freedesktop](https://junglewise.ai/threats/vendors/freedesktop).

## Quick answers

**Is CVE-2026-94286 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-94286 being exploited in the wild.

**How severe is CVE-2026-94286?** High severity, with a CVSS score of 7.1, published 28 September 2026.

**Which products and versions are affected?** Freedesktop libXtst before 1.2.6.

**Is there a fix for CVE-2026-94286?** A patch was published on 2026-09-23: Merge request merged on September 23, 2026 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-94286 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-94286?** Check whether you run Freedesktop libXtst at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The RECORD reply parser in libXtst performs insufficient validation of the datum_bytes field claimed by a reply element against the actual reply buffer size. An attacker controlling a malicious X server can construct a RECORD reply where the declared element size exceeds the remaining buffer, resulting in an out-of-bounds read. The vulnerability requires an X client to connect to and trust the malicious server.

## Affected products

- freedesktop libXtst before 1.2.6

## Timeline

- 2026-09-28: disclosed
- 2026-09-23: patched: Merge request merged on September 23, 2026

## References

- [https://gitlab.freedesktop.org/xorg/lib/libxtst/-/merge_requests/10/diffs?commit_id=16023c86070e6af9407330deea3938fcef75815b](https://gitlab.freedesktop.org/xorg/lib/libxtst/-/merge_requests/10/diffs?commit_id=16023c86070e6af9407330deea3938fcef75815b)

## Related threats

- [libXtst infinite loop in RECORD EnableContext reply parsing](https://junglewise.ai/threats/cve-2026-109088-a-malicious-x-server-could-send-malformed-record-enablecontext)