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Improper LockingWeakness · CWE-667

CVE-2026-42489

MEDIUM · 5.3 CVSS v3.1 Published 2026-06-18
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
55/100
Remediation priority · Elevated
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
[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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

This is a locking fairness issue in the Xen hypervisor's domctl operations used for guest creation and management. The system-wide lock used to serialize certain operations does not provide fairness guarantees, meaning some operations could be delayed or starved indefinitely under contention. The CVSS 5.3 indicates moderate local/adjacent impact, likely enabling denial of service through resource starvation.

MitigationApply the Xen hypervisor security patches for CVE-2026-42489 once available; until then, monitor domctl operation latency and consider limiting the rate of concurrent guest management operations to reduce lock contention.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
High
Privileges
High
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify if Xen hypervisor is running
    Run 'xl info' or 'xm info' to display hypervisor information. Check for 'Xen' in the hypervisor row.
    Affected if The system is running a Xen hypervisor and the command returns Xen-specific information
  2. Determine the installed Xen hypervisor version
    Run 'xl info | grep xen_version' or check /sys/hypervisor/version if available. Compare the version number against any Xen security advisories for CVE-2026-42489.
    Affected if The Xen version matches the affected versions listed in Xen security advisories for this CVE (if version ranges become available)
  3. Confirm domctl operations are in use
    Monitor for domctl-related system calls or check for active guest management operations using 'xl list' or 'xm list'. domctl is used for domain control operations.
    Affected if The system is actively managing Xen guests (domains) using domctl interface
  4. Check for lock contention indicators
    Use 'xl top' or 'xm top' to observe CPU usage and operation latency. Review Xen hypervisor logs (xm dmesg or xl dmesg) for any lock-related warnings or stalls during guest management operations.
    Affected if Operations show unusual latency or there are log entries indicating lock contention during domctl operations
  5. Monitor guest management operation latency
    Measure the time taken for guest lifecycle operations (create, shutdown, pause). Look for operations that take significantly longer than expected or hang.
    Affected if Guest management operations experience delays or timeouts under concurrent load, suggesting lock starvation

A defender is affected if they are running a Xen hypervisor version known to be vulnerable to CVE-2026-42489 and actively using domctl operations for guest management where lock contention can cause denial of service.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the Xen hypervisor security patches for CVE-2026-42489 once available; until then, monitor domctl operation latency and consider limiting the rate of concurrent guest management operations to reduce lock contention.

Have this fixed Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing6.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,220
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-42489 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
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  • Version or environment caveats, and links to real fixes
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