# CVE-2026-34003: X.Org X server out-of-bounds memory access in XKB request validation

Source: https://junglewise.ai/threats/cve-2026-34003-x-org-x-server-out-of-bounds-memory-access-in-xkb-request  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-23. Updated: 2026-05-19  
License: CC BY 4.0 with a link back

CVE-2026-34003 · Severity: high · CVSS 7.8 · Published 2026-04-23

A security vulnerability has been identified in the X.Org X server, a fundamental component used to manage graphical displays and user input on Linux systems. A local user could exploit this flaw to crash the system or potentially access sensitive information stored in memory. This could lead to a disruption of services or unauthorized data exposure on affected workstations and servers.

Technologies: [Tigervnc](https://junglewise.ai/threats/technologies/tigervnc), [X.Org Foundation X Server](https://junglewise.ai/threats/technologies/x-server), [X.Org Foundation Xwayland](https://junglewise.ai/threats/technologies/xwayland). Vendors: [Tigervnc](https://junglewise.ai/threats/vendors/tigervnc), [X.Org Foundation](https://junglewise.ai/threats/vendors/x-org-foundation).

## Quick answers

**Is CVE-2026-34003 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-34003 being exploited in the wild.

**How severe is CVE-2026-34003?** High severity, with a CVSS score of 7.8, published 23 April 2026.

**Which products and versions are affected?** X.Org Foundation X Server All versions prior to April 2026 patches.

**Is there a fix for CVE-2026-34003?** A patch was published on 2026-04-27: Red Hat released security updates for RHEL 9 (RHSA-2026:10739) Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-34003 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2026-34003?** Check whether you run Tigervnc, X.Org Foundation X Server or X.Org Foundation Xwayland 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

An out-of-bounds (OOB) read vulnerability (CWE-125) exists in the X.Org X server's XKB (X Keyboard Extension) key types request validation logic. The flaw is triggered when the server processes a specially crafted XKB request from a local client. Because the server fails to properly validate the request parameters, it may access memory outside of the intended buffer. This can result in a server crash (Denial of Service) or the exposure of sensitive memory contents to the local attacker. The vulnerability affects standard X.Org servers, Xwayland, and TigerVNC components that incorporate X server code. Patches have been released by major distributions including Red Hat.

## Affected products

- X.Org X server All versions prior to April 2026 patches
- X.Org Xwayland
- TigerVNC TigerVNC

## Timeline

- 2026-04-23: disclosed: CVE published and reported by Red Hat
- 2026-04-27: patched: Red Hat released security updates for RHEL 9 (RHSA-2026:10739)
- 2026-04-28: patched: Red Hat released security updates for RHEL 10 (RHSA-2026:11352)

## References

- [https://access.redhat.com/errata/RHSA-2026:10739](https://access.redhat.com/errata/RHSA-2026:10739)
- [https://access.redhat.com/errata/RHSA-2026:11352](https://access.redhat.com/errata/RHSA-2026:11352)
- [https://access.redhat.com/errata/RHSA-2026:11369](https://access.redhat.com/errata/RHSA-2026:11369)
- [https://access.redhat.com/errata/RHSA-2026:11388](https://access.redhat.com/errata/RHSA-2026:11388)
- [https://access.redhat.com/errata/RHSA-2026:11656](https://access.redhat.com/errata/RHSA-2026:11656)
- [https://access.redhat.com/errata/RHSA-2026:11692](https://access.redhat.com/errata/RHSA-2026:11692)
- [https://access.redhat.com/errata/RHSA-2026:13414](https://access.redhat.com/errata/RHSA-2026:13414)

## Related threats

- [X.Org X Server double free in XKB SetGeometry](https://junglewise.ai/threats/cve-2026-88812-a-double-free-in-xkb-setgeometryin-x-org-x-server-before-21-1-25)
- [X.Org X server use-after-free in SyncChangeCounter](https://junglewise.ai/threats/cve-2026-50261-x-org-x-server-use-after-free-in-syncchangecounter)
- [X.Org X server and Xwayland use-after-free in FreeCounter](https://junglewise.ai/threats/cve-2026-50260-x-org-x-server-and-xwayland-use-after-free-in-freecounter)
- [X.Org X server stack buffer overflow in XKB SetMap request](https://junglewise.ai/threats/cve-2026-50259-x-org-x-server-stack-buffer-overflow-in-xkb-setmap-request)
- [X.Org X server out-of-bounds read in XKB geometry processing](https://junglewise.ai/threats/cve-2026-34000-x-org-x-server-out-of-bounds-read-in-xkb-geometry-processing)