# CVE-2026-96423: Wireshark X11 dissector out-of-bounds heap read

Source: https://junglewise.ai/threats/cve-2026-96423-x11-protocol-dissector-crash-in-4-6-0-to-4-6-8-and-4-4-0-to-4-4  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-29. Updated: 2026-09-29  
License: CC BY 4.0 with a link back

CVE-2026-96423 · Severity: medium · CVSS 5.5 · Published 2026-09-29

The X11 protocol dissector in Wireshark—a tool used to analyze network traffic—contains a memory access vulnerability that can crash the application or disclose heap memory contents. An attacker can craft a malicious network capture file that triggers an out-of-bounds read when opened in Wireshark, leading to denial of service or information leakage without requiring any user interaction beyond opening the file.

Technologies: [Wireshark Foundation Wireshark](https://junglewise.ai/threats/technologies/wireshark-foundation-wireshark). Vendors: [Wireshark Foundation](https://junglewise.ai/threats/vendors/wireshark-foundation).

## Quick answers

**Is CVE-2026-96423 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-96423 being exploited in the wild.

**How severe is CVE-2026-96423?** Medium severity, with a CVSS score of 5.5, published 29 September 2026.

**Which products and versions are affected?** Wireshark Foundation Wireshark 4.6.0 to 4.6.8, 4.4.0 to 4.4.18.

**Is there a fix for CVE-2026-96423?** A patch was published on 2026-09-29: fixed in 4.6.9 and 4.4.19 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-96423 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-96423?** Check whether you run Wireshark Foundation Wireshark 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 X11 dissector maintains a per-conversation cache of keysym arrays, each allocated with a message-specific width, but tracks only a single scalar width value. The X_ChangeKeyboardMapping request updates cache entries independently without updating the scalar, while X_GetKeyboardMapping reply updates only the scalar, causing divergence. When KeyPress/KeyRelease events are dissected, the keycode2keysymString() function indexes cached arrays using the out-of-sync scalar width without bounds checking, resulting in heap buffer over-read from narrower arrays.

## Affected products

- Wireshark Foundation Wireshark 4.6.0 to 4.6.8, 4.4.0 to 4.4.18

## Timeline

- 2026-09-23: disclosed
- 2026-09-29: advisory: wnpa-sec-2026-108 published
- 2026-09-29: patched: fixed in 4.6.9 and 4.4.19

## References

- [https://gitlab.com/wireshark/wireshark/-/work_items/21563](https://gitlab.com/wireshark/wireshark/-/work_items/21563)
- [https://www.wireshark.org/security/wnpa-sec-2026-108.html](https://www.wireshark.org/security/wnpa-sec-2026-108.html)

## Related threats

- [Wireshark Frame protocol metadissector crash](https://junglewise.ai/threats/cve-2026-96422-frame-protocol-metadissector-crash-in-4-6-0-to-4-6-8-and-4-4-0-to)
- [Wireshark Toshiba file parser crash](https://junglewise.ai/threats/cve-2026-96420-toshiba-file-parser-crash-in-4-6-0-to-4-6-8-and-4-4-0-to-4-4-18)
- [Wireshark profile import path traversal code execution](https://junglewise.ai/threats/cve-2026-96419-profile-import-crash-in-4-6-0-to-4-6-8-and-4-4-0-to-4-4-18-allows)
- [Wireshark TIFF dissector infinite loop](https://junglewise.ai/threats/cve-2026-96418-tiff-protocol-dissector-infinite-loop-in-4-6-0-to-4-6-8-and-4-4-0)
- [Wireshark RF4CE protocol dissector buffer overflow](https://junglewise.ai/threats/cve-2026-96417-rf4ce-protocol-dissector-crash-in-4-6-0-to-4-6-8-and-4-4-0-to-4-4)