Medium [CVE-2026-56000] GLX contextTags Use-After-Free in CommonMakeCurrent

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.

A flaw was found in the X.org X11 server, specifically within the GLX (OpenGL Extension to the X Window System) dispatch layer. A remote attacker can exploit this vulnerability by sending a series of crafted X11 requests.

This can lead to a use-after-free condition, where the server attempts to write data to memory that has already been released. The primary consequence of this memory corruption is a denial of service, potentially causing the X server to crash.

An Important use-after-free vulnerability in the X.org X11 server's GLX dispatch layer allows a remote, unauthenticated attacker to trigger a denial of service. This is considered Important due to the remote attack vector and the potential for unauthenticated denial of service.

Red Hat severity: Important — CVSS 6.5 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H). Weakness: CWE-825.

Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 10.0 Extended Update Support; Red Hat Enterprise Linux 9; Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions; Red Hat Enterprise Linux 9.6 Extended Update Support; Red Hat Enterprise Linux 8.