# CVE-2026-88807: libXrender heap overflow in RenderQueryPictFormats

Source: https://junglewise.ai/threats/cve-2026-88807-a-heap-overflow-in-libxrender-before-0-9-13-in  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-21. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-88807 · Severity: info · Published 2026-09-21

libXrender is an X Window System library that handles rendering operations for graphical applications. A heap overflow vulnerability in the RenderQueryPictFormats function allows a malicious X server to write beyond allocated memory, potentially enabling code injection into X client processes that connect to it. This could give an attacker complete control over any X applications running on a system.

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

## Quick answers

**Is CVE-2026-88807 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-88807 being exploited in the wild.

**How severe is CVE-2026-88807?** Informational severity, published 21 September 2026.

**Which products and versions are affected?** X.Org Foundation libXrender before 0.9.13.

**Is there a fix for CVE-2026-88807?** A patch was published on 2026-09-18: Fix merged in libXrender repository Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-88807 attacked?** It is attacked over the network or from the adjacent network, in a software library.

**Am I affected by CVE-2026-88807?** Check whether you run X.Org Foundation libXrender 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 vulnerability occurs in RenderQueryPictFormats when a malicious X server sends a response with a numSubpixels count greater than numScreens, causing out-of-bounds writes to the screen->subpixel buffer allocated based on the actual screen count. The attack requires a compromised or attacker-controlled X server to which a client connects, enabling arbitrary code execution within the context of the client application.

## Affected products

- X.Org Foundation libXrender before 0.9.13

## Timeline

- 2026-09-21: disclosed
- 2026-09-18: patched: Fix merged in libXrender repository

## References

- [https://gitlab.freedesktop.org/xorg/lib/libxrender/-/merge_requests/19](https://gitlab.freedesktop.org/xorg/lib/libxrender/-/merge_requests/19)