# CVE-2026-42489: domctl lock open to abuse

> An attacker can abuse the domctl system-wide lock to cause a denial of service by preventing fair access to hypervisor operations.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Jun 2026
- **Updated:** 18 Jun 2026
- **Also known as:** ALPINE-CVE-2026-42489, DEBIAN-CVE-2026-42489, GHSA-vw8q-74w5-57vq, UBUNTU-CVE-2026-42489

## What is CVE-2026-42489?

CVE-2026-42489 is a medium-severity denial of service vulnerability in Xen, published on 18 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

[This CNA information record relates to multiple CVEs; the
text explains which aspects/vulnerabilities correspond to which CVE.]

To create and manage guests, domctl operations are used by the control
domain, a possible Xenstore domain, or by a domain controlling a
particular guest.  Some of these operations may not be executed in
parallel, so a system-wide lock is used.  The way that lock is acquired
is, however, not providing any fairness.  This is CVE-2026-42489.

Furthermore, with XSM/Flask in use, the lock acquire will, for some
operations, occur ahead of any permission checking.  This is
CVE-2026-42490.

Weakness: CWE-667 (Improper Locking)

## Which versions are affected by CVE-2026-42489?


## How do I fix CVE-2026-42489?

Apply the vendor's patch.

## Is CVE-2026-42489 being exploited?

There is no known exploitation of CVE-2026-42489 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42489 and fix it if it is affected.

What it is: CVE-2026-42489 is a medium-severity denial of service vulnerability in Xen, published on 18 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-2026-42489 in the wild and no public exploit code.

Affected product: Xen. 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-2026-42489/ (Markdown: https://insights.sbomify.com/CVE-2026-42489/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42489
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42489
- OSV: https://osv.dev/vulnerability/CVE-2026-42489

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42489/
Summaries are generated and may contain mistakes; the official description above is the record.