# CVE-2026-93542: libXi out-of-bounds read in XI2 class parsing

Source: https://junglewise.ai/threats/cve-2026-93542-an-out-of-bounds-read-in-libxi-s-xi2-class-parsing-via-size  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-24. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-93542 · Severity: medium · CVSS 6.5 · Published 2026-09-24

libXi is a library that handles input device communication in X11 graphical systems. A flaw in how it parses device class information from untrusted X servers could allow a malicious server to crash X client applications. This could be exploited to cause denial of service on systems using compromised or attacker-controlled X servers.

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

## Quick answers

**Is CVE-2026-93542 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-93542 being exploited in the wild.

**How severe is CVE-2026-93542?** Medium severity, with a CVSS score of 6.5, published 24 September 2026.

**Which products and versions are affected?** X.Org libXi before 1.8.4.

**Is there a fix for CVE-2026-93542?** A patch was published on 2026-09-23: Fix merged in GitLab merge request !23 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-93542 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-93542?** Check whether you run X.Org libXi 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 read vulnerability exists in the size_classes() and copy_classes() functions when parsing XI2 device class information, triggered via improper bounds checking of class header data. The vulnerability is triggered by network input from an X server without proper validation of message boundaries. A malicious X server can craft a specially formatted reply to trigger the out-of-bounds read, causing a crash of the client application.

## Affected products

- X.Org libXi before 1.8.4

## Timeline

- 2026-09-24: disclosed
- 2026-09-23: patched: Fix merged in GitLab merge request !23

## References

- [https://gitlab.freedesktop.org/xorg/lib/libxi/-/merge_requests/23/diffs?commit_id=f499944ad595b9bd7e7571c810842244caf150aa](https://gitlab.freedesktop.org/xorg/lib/libxi/-/merge_requests/23/diffs?commit_id=f499944ad595b9bd7e7571c810842244caf150aa)

## Related threats

- [libXi heap overflow in DEVICE_ENABLE reply handling](https://junglewise.ai/threats/cve-2026-109090-a-malicious-x-server-could-cause-a-heap-overflow-by-injecting-a)
- [libXi heap buffer overflow in DEVICE_RESOLUTION handling](https://junglewise.ai/threats/cve-2026-109089-a-buffer-overflow-when-handling-device-resolution-in-libxi)
- [libXi out-of-bounds read in XListInputDevices() class parsing](https://junglewise.ai/threats/cve-2026-94281-an-out-of-bounds-read-in-libxi-s-xlistinputdevices-class-parsing)
- [libXi out-of-bounds read in XI2 XIQueryDevice reply parsing](https://junglewise.ai/threats/cve-2026-93544-an-out-of-bounds-read-in-libxi-s-xi2-xiquerydevice-reply-parsing)
- [libXi out-of-bounds read in XI2 class parser](https://junglewise.ai/threats/cve-2026-93543-an-out-of-bounds-read-in-libxi-s-xi2-class-parser-in-libxi-before)