CVE-2026-56003: libXfont2 computeProps Property Buffer Heap Buffer Overflow

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-08 · updated 2026-10-25
Weakness: CWE-122

Description

A heap buffer overflow due to missing size checking in the property buffer when parsing PCF files in libXfont2 ComputeScaledProperties() before libXfont2 before 2.0.8 could be used by attackers using authenticated X clients to execute code within the X server.

Affected products

X.Org libXfont2: from 2.0.0 before 2.0.8 — fixed in 2.0.8

How to fix

Upgrade to a fixed version: X.Org libXfont2 2.0.8. Check the vendor advisory for mitigations.

References

https://gitlab.freedesktop.org/xorg/lib/libxfont/-/commit/dff957a5158da038a282a59a31fe736702732939
https://www.openwall.com/lists/oss-security/2026/07/08/1

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