Skip to main content
View

Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Recon
    Obtain local shell on RHEL host
  2. Delivery
    Connect to X server socket as user
  3. Exploit
    Create multiple SyncCounters via XSync
  4. Install
    Open second client and race ChangeCounter against destroy
  5. C2
    Trigger use-after-free in SyncChangeCounter()
  6. Execute
    Hijack control flow inside X server
  7. Impact
    Execute code as root or crash display

Vulnerability Assessment

Weakness
CWE
CWE-416
ASVS 5.0
V15 - Secure Coding and Architecture Memory lifecycle management
MITRE ATT&CK

2 techniques across 2 tactics: Execution, Privilege Escalation

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Sign in to read
Exploitation Conditions

Attacker must already have local code execution as any user account with permission to open the X server's UNIX socket (i.e., a logged-in session user or any process running under that user's UID), and the target host must be running X.Org Server or Xwayland with the XSync extension enabled (the default). Two concurrent X11 client connections are required to win the race between SyncCounter destruction and ChangeCounter mutation, and root-equivalent privilege escalation only occurs when the X server itself runs as root - typical on legacy Xorg deployments on RHEL 6/7 and some RHEL 8 setups, but not on rootless Xorg or Xwayland-under-Wayland configurations where impact is bounded to the user's session. No user interaction by the victim is required (UI:N), no network reachability is needed (AV:L), and no special non-default configuration is required beyond Xorg/Xwayland being installed and running.
Impact

The CVSS 3.1 vector AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H scores 7.8 and accurately describes the threat: a local, low-privileged user can reliably drive the race with no user interaction, and impact is full C/I/A compromise of the X server process. Where the server runs as root (classic Xorg on RHEL 6/7 and many RHEL 8 configurations), this becomes a clean local privilege escalation; under Xwayland or rootless Xorg the worst-case is typically a session-level DoS plus same-user code execution. EPSS, KEV, and SSVC data were not provided in the input, so prioritization must rely on CVSS and exposure: this is a real priority on multi-user Linux hosts, jump boxes, and shared developer/CI systems, and a lower priority on single-user desktops or headless servers where Xorg is not installed. No public exploit identified at time of analysis, which slightly reduces urgency but does not change the patch recommendation given the straightforward race-condition primitive.
Exploit ScenarioDerived

A local low-privileged user on a RHEL workstation or jump host opens two X11 client connections to the running display: the first creates several SyncCounter objects via the XSync extension, and the second races to destroy them while the first is issuing ChangeCounter requests, triggering the use-after-free in SyncChangeCounter(). With a well-shaped heap the attacker turns the dangling pointer into arbitrary code execution inside the X server process, gaining root on systems where Xorg still runs as root, or at minimum crashing the display and disrupting all GUI sessions. No public exploit identified at time of analysis, but the primitive - a classic race-to-free on a refcounted X resource - is well within reach of an experienced exploit developer.
This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
No patch listed yet 0.0% exploitation probability (EPSS)

Get an e-mail when this CVE is exploited, patched or re-scored. Free account.

Alert me

AnalysisAIv1 – Jun 05, 2026

Local privilege escalation in the X.Org X server and Xwayland arises from a use-after-free in SyncChangeCounter() that a local authenticated attacker can trigger by orchestrating two client connections - one creating multiple SyncCounters, the other destroying them while they are being changed. On systems where the X server still runs as root (common on legacy Linux setups), successful exploitation yields root code execution; at minimum it crashes the display server. No public exploit identified at time of analysis, but the bug is confirmed by Red Hat and a fix has landed upstream in xserver.

RemediationAI

Apply the vendor-released X.Org/Xwayland updates as soon as Red Hat publishes per-RHEL-stream errata referenced from https://access.redhat.com/security/cve/CVE-2026-50261 (track Bugzilla https://bugzilla.redhat.com/show_bug.cgi?id=2485386 for RHSA links); upstream the fix is commit bdd7bf57af208b1ddf57d4683d67104443b44812 on gitlab.freedesktop.org/xorg/xserver, announced at https://lists.x.org/archives/xorg-announce/2026-June/003702.html. Until patches are installed, reduce risk by switching to Wayland sessions with Xwayland where feasible, ensuring Xorg is not configured to run as root (use rootless Xorg via systemd-logind on RHEL 8+ - note this disables some legacy proprietary drivers), restricting interactive shell access on multi-user hosts so untrusted local users cannot reach the X server socket, and removing xorg-x11-server packages entirely from headless servers where they were installed unnecessarily.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Sign in to check
Technical ContextAI · show details

The vulnerability lives in the XSync extension of xorg-server/Xwayland (CWE-416, Use-After-Free) inside SyncChangeCounter(), the handler responsible for updating SyncCounter objects used for client synchronization primitives. Because two distinct X11 client connections can race against the same counter - one connection destroying it while another mutates it - the server dereferences a freed SyncCounter object. The affected CPE set (Red Hat Enterprise Linux 6 through 10) reflects that all currently supported and legacy RHEL streams ship a vulnerable xorg-server/xwayland package; the upstream fix commit bdd7bf57af208b1ddf57d4683d67104443b44812 in freedesktop.org's xserver repository addresses the lifecycle bug.

Know when Red Hat Enterprise Linux 10 gets its next vulnerability

  • Watch products and get an email when something new is published
  • Check this CVE against your own stack and servers
  • Exploit and PoC references, threat intelligence from 22 sources
Continue with Google Continue with GitHub

No credit card · 7-day full trial

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
Red Hat 7.8 HIGH

Primary rating from Vendor (redhat).

CVSS VectorVendor: redhat

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

DescriptionCVE.org

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

Zero Day Initiative Advisories

ZDI-26-395 X.Org Server SyncChangeCounter Use-After-Free Privilege Escalation Vulnerability Jun 2026

Executive ViewAI

Why It Matters

X.Org X server and Xwayland contain a local privilege escalation vulnerability (CVE-2026-50261, CVSS 7.8) exploitable by authenticated system users through a use-after-free flaw. On legacy Linux deployments where the X server retains root privileges, successful exploitation grants root-level code execution; affected systems will experience at minimum display server crashes with service disruption.

Business Impact: High
Compensating Controls

No vendor-released patch identified at time of analysis. Fix available upstream in xserver repository. Interim mitigations: (1) reconfigure X server to run with least privilege under non-root user context where architecture permits; (2) enforce host-level access controls limiting local login to authorized personnel only; (3) monitor Red Hat and upstream xserver repositories for official patch availability; (4) consider migration to Wayland-based compositors on affected systems.

Threat Intelligence Overview

EPSS Score
0.0%
Top 98% exploitable
Data Quality
7 sources
Confidence: High
EUVD NVD CVE.org EPSS Vulnrichment MSRC Vendor VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC No
EPSS 0.0%
Patch available No
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision
Scheduled
Exploitation
None
System Exposure· derived
Small
Automatable
No
Human Impact
High
Technical Impact
Total

Priority Score

39
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +39
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Privilege Escalation HIGH

Privilege escalation occurs when an attacker leverages flaws in access control mechanisms to gain permissions beyond what they were originally granted.

Use After Free HIGH

Use-after-free vulnerabilities occur when a program continues to access memory through a pointer after that memory has been deallocated.

Memory Corruption HIGH

Memory corruption occurs when a program writes data beyond the boundaries of allocated memory regions or accesses memory in unintended ways, violating the integrity of the process's address space.

Affected Products (CPE)CVE.org

cpe:2.3:a:red_hat:red_hat_enterprise_linux_10:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_6:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_7:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_8:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_8:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_9:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_9:*:*:*:*:*:*:*:*

More in Red Hat Enterprise Linux 10

View all
CVE-2026-18663 MEDIUM
5.9 Aug 12

Heap corruption via double-free in 389-ds-base's LDAP control parsing allows an unauthenticated remote attacker to crash
CVE-2026-4631 CRITICAL POC
9.8 Apr 07

Remote code execution in Cockpit's web interface allows unauthenticated attackers to execute arbitrary commands on the h
CVE-2026-4480 CRITICAL POC
9.0 May 26

Remote code execution in Samba's printing subsystem allows remote attackers to inject arbitrary shell commands via craft
CVE-2026-101258 HIGH POC
7.8 Oct 06

Ghostscript can execute arbitrary shell commands with the privileges of its process when it renders a crafted PostScript
CVE-2026-96889 HIGH POC
7.8 Sep 23

Use-after-free in librsvg during rendering of crafted SVG documents with nested XInclude directives and duplicate entity
CVE-2026-4775 HIGH POC
7.8 Mar 24

A signed integer overflow vulnerability exists in the libtiff library's putcontig8bitYCbCr44tile function that leads to

CVE-2026-114406 MEDIUM POC
6.8 Oct 21

The system CA trust store shipped in Red Hat's ca-certificates RPM packages includes eMudhra root authorities that signe
CVE-2026-18922 CRITICAL
9.8 Sep 07

Authentication bypass in 389 Directory Server (shipped as Red Hat Directory Server 11-13 and within RHEL 6-10) lets remo
CVE-2026-14544 CRITICAL
9.8 Jul 03

Remote code execution and privilege escalation in HPLIP (HP Linux Imaging and Printing) affects the hpcups print filter

CVE-2026-76578 CRITICAL
9.8 Sep 07

Unauthenticated privilege escalation in FreeIPA (Red Hat Identity Management) allows a remote attacker to gain genuine a
CVE-2026-102560 CRITICAL
9.8 Sep 29

A heap buffer overflow exists in libsoup's WebSocket permessage-deflate compression path: when a very large outbound mes
CVE-2026-5121 HIGH
7.5 Mar 30

Remote code execution in libarchive on 32-bit systems allows unauthenticated attackers to execute arbitrary code via spe

Same weakness CWE-416 – Use After Free

View all
CVE-2019-0708 CRITICAL POC
9.8
CVE-2015-5119 CRITICAL POC
9.8
CVE-2014-0322 HIGH POC
8.8
CVE-2012-4792 HIGH POC
8.8
CVE-2009-4324 HIGH POC
7.8
CVE-2015-0313 CRITICAL POC
9.8
CVE-2015-5122 CRITICAL POC
9.8
CVE-2013-2551 HIGH POC
8.8

Same technique Privilege Escalation

View all
CVE-2024-0012 CRITICAL POC
9.3
CVE-2025-47812 CRITICAL POC
10.0
CVE-2013-0422 CRITICAL POC
9.8
CVE-2013-0632 CRITICAL POC
9.8
CVE-2024-9474 MEDIUM POC
6.9
CVE-2017-5689 CRITICAL POC
9.8
CVE-2021-20021 CRITICAL POC
9.8
CVE-2017-12635 CRITICAL POC
9.8

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

References

Advisories & patches
ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-50261 ADVISORY https://vuldb.com/vuln/368917 REF https://access.redhat.com/errata/RHSA-2026:26562 REF https://access.redhat.com/errata/RHSA-2026:26566 REF https://access.redhat.com/errata/RHSA-2026:26590 REF https://access.redhat.com/errata/RHSA-2026:26610 REF https://access.redhat.com/errata/RHSA-2026:26709 REF https://access.redhat.com/errata/RHSA-2026:28923 REF https://access.redhat.com/errata/RHSA-2026:29844 REF https://access.redhat.com/errata/RHSA-2026:36083 REF https://access.redhat.com/errata/RHSA-2026:36085 REF https://access.redhat.com/errata/RHSA-2026:36086 REF https://access.redhat.com/errata/RHSA-2026:36087 REF https://access.redhat.com/errata/RHSA-2026:36632 REF https://access.redhat.com/errata/RHSA-2026:36633 REF https://access.redhat.com/errata/RHSA-2026:36634 REF https://access.redhat.com/errata/RHSA-2026:36768 REF https://access.redhat.com/errata/RHSA-2026:36791 REF https://access.redhat.com/errata/RHSA-2026:36792 REF https://access.redhat.com/errata/RHSA-2026:36798 REF https://access.redhat.com/errata/RHSA-2026:38502 REF https://access.redhat.com/errata/RHSA-2026:38810 REF https://access.redhat.com/errata/RHSA-2026:46377 REF https://access.redhat.com/errata/RHSA-2026:46382 REF https://access.redhat.com/errata/RHSA-2026:46385 REF https://access.redhat.com/errata/RHSA-2026:46392 REF https://access.redhat.com/errata/RHSA-2026:46456 REF https://access.redhat.com/errata/RHSA-2026:46460 REF https://access.redhat.com/errata/RHSA-2026:46473 REF https://access.redhat.com/errata/RHSA-2026:49519 REF https://access.redhat.com/security/cve/CVE-2026-50261 REF https://bugzilla.redhat.com/show_bug.cgi?id=2485386 REF https://gitlab.freedesktop.org/xorg/xserver/-/commit/bdd7bf57af208b1ddf57d4683d67104443b44812 REF https://lists.x.org/archives/xorg-announce/2026-June/003702.html REF https://redhat.atlassian.net/browse/PSIRTSUPT-16950 REF https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-50261.json

Search Externally

GitHub PoC Exploit-DB PacketStorm Snyk Rapid7 Nuclei Templates Trickest PoC
Back

This site uses cookies essential for authentication and security. No tracking or analytics cookies are used. Privacy Policy