# CVE-2026-94285: libX11 out-of-bounds read in codeset parser

Source: https://junglewise.ai/threats/cve-2026-94285-an-out-of-bounds-read-in-libx11-s-byte-oriented-codeset-parser-in  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-28. Updated: 2026-09-28  
License: CC BY 4.0 with a link back

CVE-2026-94285 · Severity: medium · CVSS 5.1 · Published 2026-09-28

libX11 is a core X Window System library that X clients use to communicate with X servers. A malicious X server can trigger an out-of-bounds memory read in libX11's codeset parser, crashing any client connected to it. This affects any graphical application using X11 on vulnerable systems.

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

## Quick answers

**Is CVE-2026-94285 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-94285 being exploited in the wild.

**How severe is CVE-2026-94285?** Medium severity, with a CVSS score of 5.1, published 28 September 2026.

**Which products and versions are affected?** X.Org Foundation libX11 before 1.8.14.

**Is there a fix for CVE-2026-94285?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-94285 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-94285?** Check whether you run X.Org Foundation libX11 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 byteM_parse_codeset() function within libX11's byte-oriented codeset parser (lcGenConv.c). The vulnerability occurs when the parser fails to validate buffer bounds before reading character data. The fix adds a remaining_bytes parameter to track available input and skips parsing if the codeset length exceeds the remaining buffer.

## Affected products

- X.Org Foundation libX11 before 1.8.14

## Timeline

- 2026-09-28: disclosed

## References

- [https://gitlab.freedesktop.org/xorg/lib/libx11/-/merge_requests/310/diffs?commit_id=980868483446f24f9658d26aa5bfa42f3da6dd3a](https://gitlab.freedesktop.org/xorg/lib/libx11/-/merge_requests/310/diffs?commit_id=980868483446f24f9658d26aa5bfa42f3da6dd3a)