# CVE-2026-50261: Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: use-after-free in syncchangecounter()

> A use-after-free in X.Org X server allows attackers to crash the server or escalate privileges if running as root.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 5 Jun 2026
- **Updated:** 28 Sep 2026
- **Also known as:** AZL-89540, AZL-89568, BELL-CVE-2026-50261, DEBIAN-CVE-2026-50261, ECHO-7923-725c-f8c4, GHSA-4r2h-m6wp-gxg9, UBUNTU-CVE-2026-50261

## What is CVE-2026-50261?

CVE-2026-50261 is a high-severity use after free vulnerability in Redhat Enterprise Linux, published on 5 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-50261?

It affects 3 products.


Products: Redhat Enterprise Linux, X.org X Server, X.org Xwayland.

## How do I fix CVE-2026-50261?

Apply the vendor's patch.

## Is CVE-2026-50261 being exploited?

There is no known exploitation of CVE-2026-50261 in the wild and no public exploit code.

## Other vulnerabilities in Redhat Enterprise Linux

- [CVE-2018-14667](https://insights.sbomify.com/CVE-2018-14667/): Red Hat JBoss RichFaces Framework Expression Language Injection (critical 9.8, exploited in the wild)
- [CVE-2021-20325](https://insights.sbomify.com/CVE-2021-20325/): Missing fixes for CVE-2021-40438 and CVE-2021-26691 in the versions of httpd, as shipped in Red Hat Enterprise Linux 8.5.0, causes a securit (critical 9.8)
- [CVE-2018-25011](https://insights.sbomify.com/CVE-2018-25011/): Memory corruption in libwebp (critical 9.8)
- [CVE-2018-25014](https://insights.sbomify.com/CVE-2018-25014/): Other in libwebp (critical 9.8)
- [CVE-2014-3585](https://insights.sbomify.com/CVE-2014-3585/): Supply chain in redhat-upgrade-tool (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-50261 and fix it if it is affected.

What it is: CVE-2026-50261 is a high-severity use after free vulnerability in Redhat Enterprise Linux, published on 5 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-50261 in the wild and no public exploit code.

Affected product: Redhat Enterprise Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-50261/ (Markdown: https://insights.sbomify.com/CVE-2026-50261/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-50261
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-50261
- OSV: https://osv.dev/vulnerability/CVE-2026-50261

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-50261/
Summaries are generated and may contain mistakes; the official description above is the record.