# CVE-2026-93515: X.org X Server use-after-free in present_clear_window_notifies

Source: https://junglewise.ai/threats/cve-2026-93515-a-use-after-free-in-present-clear-window-notifies-in-the-x-org-x  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-28. Updated: 2026-10-28  
License: CC BY 4.0 with a link back

CVE-2026-93515 · Severity: info · Published 2026-10-28

The X.org X Server manages display rendering for graphical applications. A use-after-free vulnerability in the Present extension allows malicious X clients to crash the X server or potentially execute code with server privileges by destroying specific windows in a particular sequence.

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

## Quick answers

**Is CVE-2026-93515 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-93515 being exploited in the wild.

**How severe is CVE-2026-93515?** Informational severity, published 28 October 2026.

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

**Is there a fix for CVE-2026-93515?** 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-2026-93515 attacked?** It is attacked with local access, in a hosted service.

**Am I affected by CVE-2026-93515?** Check whether you run X.Org X Wayland or X.Org X Server 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 use-after-free write occurs in present_clear_window_notifies() when cross-window Present notifies are used. When a notify-target window is destroyed while an untriggered wait_fence keeps a vblank alive, dangling pointers remain in the window notify list; subsequent vblank teardown calls present_free_window_notify() which writes through these pointers. The vulnerability requires local X protocol access.

## Affected products

- X.org X Server before 21.1.25
- X.org X Wayland before 24.1.14

## Timeline

- 2026-10-28: disclosed
- 2026-08-26: patched: Commit 1b6955c3 by Peter Hutterer

## References

- [https://gitlab.freedesktop.org/xorg/xserver/-/commit/1b6955c3108e6b43433aefe860070708e6f43d1b](https://gitlab.freedesktop.org/xorg/xserver/-/commit/1b6955c3108e6b43433aefe860070708e6f43d1b)

## Related threats

- [X.Org X Server use after free in gesture sprite lifecycle](https://junglewise.ai/threats/cve-2026-93536-a-use-after-free-caused-by-missing-lifecycle-management-of)
- [X.Org X Server buffer overread in CheckKeySyms](https://junglewise.ai/threats/cve-2026-93524-a-buffer-overread-in-checkkeysyms-in-x-org-x-server-before-21-1)
- [X.Org X Server heap buffer overflow in XIPassiveUngrabDevice](https://junglewise.ai/threats/cve-2026-93523-a-heap-buffer-overflow-caused-by-a-xipassiveungrabdevice-request)
- [X.Org X Server heap buffer overflow in CopyArea CPU-to-FBO](https://junglewise.ai/threats/cve-2026-93522-a-heap-buffer-overflow-caused-by-mismatched-size-usage-in)
- [X.Org X Server buffer overflow in RandR ChangeProviderProperty](https://junglewise.ai/threats/cve-2026-93521-a-buffer-overflow-in-randr-changeproviderproperty-requests-in-x)