CVE-2026-56000: xorg-x11-server / xwayland GLX contextTags Use-After-Free in CommonMakeCurrent()

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-08 · updated 2026-07-09
Weakness: CWE-416

Description

Local attackers with a X connection able to provide GLX commit to the X server xorg-server before 21.2.24 and xwayland before 24.1.13 could cause a Heap Use After Free, due to CommonMakeCurrent() pointing into potentially reallocated memory.

Affected products

xorg-x11-server: before 21.2.24 — fixed in 21.2.24
X.Org xwayland: before 24.1.13 — fixed in 24.1.13

How to fix

Upgrade to a fixed version: xorg-x11-server 21.2.24; X.Org xwayland 24.1.13. Check the vendor advisory for mitigations.

References

https://gitlab.freedesktop.org/xorg/xserver/-/commit/2779affbdb4354e894f490e56f962527d6125043
https://www.openwall.com/lists/oss-security/2026/07/08/2

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