dbcve.org
FreeBSDOperating system

CVE-2026-45259

MEDIUM · 6.5 CVSS v3.1 Published 2026-06-27
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
67/100
Remediation priority · Elevated
Zero-click 8 weeks old

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
sigqueue(2) was marked as permitted in capability mode with the introduction of Capsicum in 2011, but the implementation of kern_sigqueue did not include a capability mode check restricting signal delivery to the calling process's own PID. A process in capability mode can use sigqueue(2) to send signals to any process it could signal following standard Unix permissions, bypassing the Capsicum sandbox restriction. A compromised sandboxed process could interfere with other processes, for example by sending SIGKILL or SIGSTOP. This could be any process running as the same user, or any process, for a superuser sandboxed process.

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 · high confidence

In FreeBSD, sigqueue(2) was permitted in capability mode when Capsicum was introduced in 2011, but the kern_sigqueue implementation lacked a capability mode check to restrict signal delivery to the calling process's own PID. This allows sandboxed processes to send signals (including SIGKILL/SIGSTOP) to any process they could signal under standard Unix permissions, bypassing Capsicum's sandbox restrictions.

MitigationApply the FreeBSD security patch for CVE-2026-45259 which adds the missing capability mode check in kern_sigqueue to restrict signal delivery to the sandboxed process's own PID. Until patched, minimize the use of capability mode with processes that have significant Unix signal permissions.

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
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/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. Check FreeBSD version
    Run 'uname -r' or 'freebsd-version -k' to get the installed FreeBSD version
    Affected if The version is 14.3, 14.4, or 15.0
  2. Identify capability mode processes
    Search for processes that call cap_enter() or check for 'capsicum' in process capabilities using 'procstat -ac' or examining application code for Capsicum API usage
    Affected if Applications are using Capsicum capability mode (cap_enter) and have permission to send signals to other processes
  3. Verify signal permissions for sandboxed processes
    Use 'ps -o pid,ppid,comm' to identify processes in capability mode, then review their signal permissions using 'procstat -s <pid>' or audit which targets they can signal via Unix permissions
    Affected if A sandboxed process can signal processes outside its own PID (excluding root-owned or specially privileged signal restrictions)
  4. Check for sigqueue usage
    Review application code or monitor for sigqueue(2) or kill(2) system calls from sandboxed processes using dtrace, strace equivalent (truss), or system call tracing
    Affected if Sandboxed processes are actively using sigqueue to deliver signals to targets other than their own process ID

You are affected if running FreeBSD 14.3, 14.4, or 15.0 and running applications in Capsicum capability mode that can send signals to processes other than themselves.

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 FreeBSD security patch for CVE-2026-45259 which adds the missing capability mode check in kern_sigqueue to restrict signal delivery to the sandboxed process's own PID. Until patched, minimize the use of capability mode with processes that have significant Unix signal permissions.

Fix this in FreeBSD Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing12.0 h
  • Review / QA6.0 h
30.0 hours of engineering $5,120
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,192.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-45259 — 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-2026-45259 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