# CVE-2026-93523: X.Org X Server heap buffer overflow in XIPassiveUngrabDevice

Source: https://junglewise.ai/threats/cve-2026-93523-a-heap-buffer-overflow-caused-by-a-xipassiveungrabdevice-request  
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-2026-93523 · Severity: high · CVSS 7.8 · Published 2026-10-28

X.Org X Server and XWayland are display servers that manage graphics and input on Unix systems. A flaw in the X Input extension allows authenticated X clients to send specially crafted requests that trigger a heap buffer overflow, potentially crashing the server or executing code with server privileges.

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

## Quick answers

**Is CVE-2026-93523 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-93523 being exploited in the wild.

**How severe is CVE-2026-93523?** High severity, with a CVSS score of 7.8, published 28 October 2026.

**Which products and versions are affected?** X.Org X Server before 21.1.15; X.Org XWayland before 24.1.14.

**Is there a fix for CVE-2026-93523?** Yes: fixed in X Server 21.1.15 and later; XWayland 24.1.14 and later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-93523 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-93523?** Check whether you run X.Org X Server or X.Org 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.

## How to fix

- Fixed in X Server 21.1.15 and later; XWayland 24.1.14 and later

## Technical details

The XIPassiveUngrabDevice request handler fails to validate out-of-range modifier values before passing them to DeletePassiveGrabFromList(), which uses BITCLEAR(mask, modifier) on an 8-word (256-bit) heap-allocated mask. A modifier value exceeding 255 causes out-of-bounds heap access, permitting a controlled single-bit write at an attacker-chosen offset. An authenticated X client can trigger this via a crafted Xi protocol message.

## Affected products

- X.Org X Server before 21.1.15
- X.Org XWayland before 24.1.14

## Timeline

- 2026-10-28: disclosed
- 2026-08-26: patched

## References

- [https://gitlab.freedesktop.org/xorg/xserver/-/commit/37a1847a60c6799aecf163a5cfa40077a9002675](https://gitlab.freedesktop.org/xorg/xserver/-/commit/37a1847a60c6799aecf163a5cfa40077a9002675)

## 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 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)
- [X.org X server heap buffer overflow in XkbAllocNames](https://junglewise.ai/threats/cve-2026-93520-a-heap-buffer-overflow-caused-by-mismatching-size-calculations)