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X.Org X Server EUVDEUVD-2026-34816

| CVE-2026-50260 HIGH
Use After Free (CWE-416)
2026-06-05 redhat GHSA-7j37-rf7v-jf5c
7.8
CVSS 3.1 · Vendor: redhat
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Severity by source

Vendor (redhat) PRIMARY
7.8 HIGH
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SUSE
HIGH
qualitative
Red Hat
7.8 HIGH
qualitative

Primary rating from Vendor (redhat).

CVSS VectorVendor: redhat

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

2
Analysis Generated
Jun 05, 2026 - 12:21 vuln.today
CVE Published
Jun 05, 2026 - 10:36 nvd
HIGH 7.8

DescriptionCVE.org

A use-after-free flaw was found in the X.Org X server and Xwayland in FreeCounter(). A client that sets up multiple SyncCounters and awaits on those triggers can trigger a use-after-free when destroying those counters via a second client connection. This may be used to crash the server, or for privilege escalation if the X server runs as root.

AnalysisAI

Local privilege escalation in the X.Org X server and Xwayland arises from a use-after-free in FreeCounter() when SyncCounter objects are destroyed across multiple client connections. Authenticated local attackers on affected Red Hat Enterprise Linux 6 through 10 systems can crash the server or escalate to root when the X server runs with elevated privileges. No public exploit identified at time of analysis, and the issue is not listed in CISA KEV.

Technical ContextAI

The vulnerability resides in the XSync extension of the X.Org X server (xserver) and its Wayland-compatibility component Xwayland, both maintained at gitlab.freedesktop.org/xorg/xserver. SyncCounters are server-side objects exposed by the XSync protocol extension that allow clients to coordinate timing via shared counter values and triggers (alarms). The root cause is CWE-416 (Use-After-Free): when one client allocates multiple SyncCounters with pending triggers and a second client connection causes FreeCounter() to release those counters, dangling references to the freed counter memory remain reachable, allowing subsequent operations to dereference or write to freed heap memory. Exploitation primitives from use-after-free in C-based servers like xserver typically allow attacker-controlled function pointer overwrite or heap layout manipulation leading to arbitrary code execution.

RemediationAI

Upstream fix available (commit f5abfb61994471023d8c6470428c8e30c411cc0b at https://gitlab.freedesktop.org/xorg/xserver/-/commit/f5abfb61994471023d8c6470428c8e30c411cc0b); a released patched version was not independently confirmed in the supplied data, so administrators should apply Red Hat errata referenced from https://access.redhat.com/security/cve/CVE-2026-50260 once they list specific xorg-x11-server and xorg-x11-server-Xwayland package versions. As compensating controls until patched packages are deployed, prefer Wayland sessions where Xwayland runs unprivileged rather than legacy Xorg-as-root sessions (trade-off: legacy X11-only apps requiring root X features may break), restrict local interactive logins on multi-user systems via PAM/access.conf to reduce the pool of authenticated attackers (trade-off: operational friction), and where possible disable the XSync extension or block untrusted clients from connecting to the server socket using xhost/Xauthority hardening (trade-off: applications relying on XSync alarms such as some compositors and animation toolkits will degrade or fail).

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Affected
SUSE Linux Enterprise Module for Basesystem 15 SP7 Affected
SUSE Linux Enterprise Module for Development Tools 15 SP7 Affected

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EUVD-2026-34816 vulnerability details – vuln.today

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