# CVE-2026-88812: X.Org X Server double free in XKB SetGeometry

Source: https://junglewise.ai/threats/cve-2026-88812-a-double-free-in-xkb-setgeometryin-x-org-x-server-before-21-1-25  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-27. Updated: 2026-10-27  
License: CC BY 4.0 with a link back

CVE-2026-88812 · Severity: high · CVSS 7.8 · Published 2026-10-27

X.Org X Server manages keyboard layouts and graphics on Linux systems. A flaw in the XKB geometry handler allows attached clients to trigger a double-free memory error, potentially crashing the server or executing code in the X server context. This affects desktop systems and could be exploited locally by programs running on the system.

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

## Quick answers

**Is CVE-2026-88812 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-88812 being exploited in the wild.

**How severe is CVE-2026-88812?** High severity, with a CVSS score of 7.8, published 27 October 2026.

**Which products and versions are affected?** X.Org Foundation X Server before 21.1.25; X.Org Foundation X Wayland before 24.1.14.

**Is there a fix for CVE-2026-88812?** Yes: fixed in X Server 21.1.25, X Wayland 24.1.14. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-88812 attacked?** It is attacked over the network or with local access, in a hosted service.

**Am I affected by CVE-2026-88812?** Check whether you run X.Org Foundation X Server or X.Org Foundation X Wayland 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.

## How to fix

- Fixed in X Server 21.1.25, X Wayland 24.1.14

## Technical details

A double-free vulnerability exists in _CheckSetDoodad() within X.Org X Server's XKB geometry handling. When font string allocation fails during doodad text processing, the error handler frees the text pointer without NULLing it; since the doodad was already added to the geometry, subsequent cleanup via _XkbClearDoodad() frees the same dangling pointer again. Local or network-attached X clients can trigger this via malformed XKB SetGeometry requests.

## Affected products

- X.Org Foundation X Server before 21.1.25
- X.Org Foundation X Wayland before 24.1.14

## Timeline

- 2026-10-27: disclosed
- 2026-08-26: other: Fix committed

## References

- [https://gitlab.freedesktop.org/xorg/xserver/-/commit/0d1b1b0bad86c9ea2a3b7ca5a70e681dc69f1ecc](https://gitlab.freedesktop.org/xorg/xserver/-/commit/0d1b1b0bad86c9ea2a3b7ca5a70e681dc69f1ecc)

## Related threats

- [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 memory access in XKB request validation](https://junglewise.ai/threats/cve-2026-34003-x-org-x-server-out-of-bounds-memory-access-in-xkb-request)
- [X.Org X server use-after-free in miSyncTriggerFence](https://junglewise.ai/threats/cve-2026-34001-x-org-x-server-use-after-free-in-misynctriggerfence)
- [X.Org X server integer underflow in XKB compatibility map handling](https://junglewise.ai/threats/cve-2026-33999-x-org-x-server-integer-underflow-in-xkb-compatibility-map)