Quick answers
- Is CVE-2026-56003 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-56003 being exploited in the wild.
- How severe is CVE-2026-56003?
- High severity, with a CVSS score of 8.5, published 8 July 2026.
- Which products and versions are affected?
- X.Org libXfont2 before 2.0.8.
- Is there a fix for CVE-2026-56003?
- A patch was published on 2026-06-01: Fix committed to GitLab repository Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-56003 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-56003?
- Check whether you run X.Org libXfont2 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
A heap buffer overflow exists in the ComputeScaledProperties() function of libXfont2 when parsing Portable Compiled Format (PCF) files. The function allocates a fixed-size buffer of 70 slots for font properties, but the computeProps() helper fails to perform bounds checking when writing to this buffer. An attacker can provide a malicious font containing numerous duplicate properties that match entries in the fontPropTable, causing the library to write past the end of the allocated 1120-byte buffer. This can be triggered by an authenticated X client using SetFontPath and OpenFont requests. The issue is resolved in version 2.0.8 by implementing proper capacity checks during property iteration.
Affected products
- X.Org libXfont2 before 2.0.8
Timeline
- 2026-06-01: patched: Fix committed to GitLab repository
- 2026-07-08: advisory: X.Org Security Advisory released
- 2026-07-08: disclosed: Public disclosure on oss-security mailing list