dbcve.org
FreeBSDOperating system

CVE-2026-45251

HIGH · 7.8 CVSS v3.1 Published 2026-05-21
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
80/100
Remediation priority · High
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
A file descriptor can be closed while a thread is blocked in a poll(2) or select(2) call waiting for that descriptor. Because the blocked thread does not hold a reference to the underlying object, this closure may result in the object being freed while the thread remains blocked. In this situation, the kernel must remove the blocked thread from the per-object wait queue prior to freeing the object. In the case of some file descriptor types, the kernel failed to unlink blocked threads from the object before freeing it. When the blocked thread is subsequently woken, it accesses memory that has already been freed resulting in a use-after-free vulnerability. The use-after-free vulnerability may be triggered by an unprivileged local user and can be exploited to obtain superuser privileges.

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

A use-after-free vulnerability in the Linux kernel's file descriptor handling where closing an FD while a thread is blocked in poll(2) or select(2) can free the underlying object without properly unlinking the blocked thread from the wait queue. When the thread wakes, it accesses freed memory, allowing unprivileged local users to potentially escalate to root.

MitigationApply vendor-supplied kernel security patches immediately. Limit local unprivileged user access as an interim compensating control until the patch can be deployed.

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

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
FreeBSDOperating system
Affected:= 14.3= 14.4= 15.0

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
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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. Verify the operating system is FreeBSD
    Run 'uname -s' or check /etc/os-release to confirm the system is running FreeBSD
    Affected if The system is not FreeBSD (this CVE only affects FreeBSD)
  2. Determine the installed FreeBSD version
    Run 'uname -r' or 'freebsd-version -k' to obtain the running kernel version
    Affected if Unable to determine the FreeBSD version
  3. Compare version against affected ranges
    Compare the output from step 2 against the affected versions: 14.3, 14.4, and 15.0
    Affected if The installed version matches exactly 14.3, 14.4, or 15.0

The system is affected if it is running FreeBSD version 14.3, 14.4, or 15.0, as these versions contain the kernel use-after-free flaw in poll/select file descriptor handling.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply vendor-supplied kernel security patches immediately. Limit local unprivileged user access as an interim compensating control until the patch can be deployed.

Recommended fix Moderate confidence

FreeBSD 14.4-STABLE or latest 15.x stable release

  1. Back up all critical data and verify backups before proceeding
  2. Schedule a maintenance window for the system update
  3. Update the FreeBSD ports tree and packages: portsnap fetch update
  4. Upgrade FreeBSD to the latest patched release using freebsd-update or by rebuilding from source
  5. Reboot the system to load the new kernel
  6. Verify the system is running the patched kernel with: uname -r
  7. Test critical applications and services to ensure functionality
Caveat Kernel update requires system reboot; some kernel tuning parameters may have changed in the update

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in FreeBSD Scoped from the published advisory
  • Consultation8.0 h
  • Implementation32.0 h
  • Testing24.0 h
  • Review / QA12.0 h
76.0 hours of engineering $13,120
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $20,992.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-45251 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2026-45251 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data