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FreeBSDOperating system

CVE-2025-15576

HIGH · 7.5 CVSS v3.1 Published 2026-03-09
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
77/100
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
If two sibling jails are restricted to separate filesystem trees, which is to say that neither of the two jail root directories is an ancestor of the other, jailed processes may nonetheless be able to access a shared directory via a nullfs mount, if the administrator has configured one. In this case, cooperating processes in the two jails may establish a connection using a unix domain socket and exchange directory descriptors with each other. When performing a filesystem name lookup, at each step of the lookup, the kernel checks whether the lookup would descend below the jail root of the current process. If the jail root directory is not encountered, the lookup continues. In a configuration where processes in two different jails are able to exchange file descriptors using a unix domain socket, it is possible for a jailed process to receive a directory for a descriptor that is below that process' jail root. This enables full filesystem access for a jailed process, breaking the chroot. Note that the system administrator is still responsible for ensuring that an unprivileged user on the jail host is not able to pass directory descriptors to a jailed process, even in a patched kernel.

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

This FreeBSD jail escape vulnerability allows a process in one jail to gain filesystem access outside its jail root when two sibling jails share a directory via nullfs and can exchange directory descriptors through Unix domain sockets. The kernel's jail boundary check only verifies if the jail root is encountered during path lookup, but does not validate directory descriptors received through socket file descriptor passing, allowing a jailed process to obtain a handle to a directory below its own jail root.

MitigationAdministrators should avoid configuring nullfs mounts sharing directories between sibling jails with different trust levels, and ensure untrusted users cannot control file descriptor passing to jailed processes. The underlying fix requires a kernel patch from FreeBSD.

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:= 13.5= 14.3

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
Low
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
None

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

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 determine the installed FreeBSD version
    Affected if The version is 13.5 or 14.3 (exact match required)
  2. Identify nullfs mounts
    Run 'mount | grep nullfs' to list all nullfs mounts on the system
    Affected if Any nullfs mounts exist that share directories between different jails
  3. Examine jail configurations
    Check jail configuration files (typically in /etc/jail.conf or jailier config) for sibling jails that share the same directory tree via nullfs
    Affected if Two or more sibling jails (not nested) are configured to access the same host directory path through nullfs
  4. Verify FD passing capability
    Review if any service or application running in the jailed environment uses Unix domain sockets with SCM_RIGHTS for file descriptor passing (e.g., check process sockets with 'sockstat -u' or audit logs for sendmsg/recvmsg calls)
    Affected if Processes in different sibling jails can exchange file descriptors through Unix domain sockets

A user is affected if running FreeBSD 13.5 or 14.3 with nullfs mounts that share directories between sibling jails, where processes can pass directory descriptors via Unix domain sockets.

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

Administrators should avoid configuring nullfs mounts sharing directories between sibling jails with different trust levels, and ensure untrusted users cannot control file descriptor passing to jailed processes. The underlying fix requires a kernel patch from FreeBSD.

Recommended fix Moderate confidence

FreeBSD 13.5 or 14.3 (latest stable release in each respective branch)

  1. Identify current FreeBSD version using 'freebsd-version -u' or 'uname -a'
  2. Update your FreeBSD ports tree to the latest: 'portsnap fetch update'
  3. Check for available FreeBSD security advisories at https://www.freebsd.org/security/advisories/
  4. Apply the latest security patches for your release branch using 'freebsd-update fetch' and 'freebsd-update install'
  5. Reboot the system to load the patched kernel
  6. Verify the kernel is running the patched version: 'uname -a'
  7. Ensure that untrusted users cannot pass directory descriptors to jailed processes as a defense-in-depth measure
Caveat Standard FreeBSD upgrade risks apply - test in staging environment before production deployment

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

Fix this in FreeBSD Scoped from the published advisory
  • Consultation4.0 h
  • Implementation16.0 h
  • Testing8.0 h
  • Review / QA4.0 h
32.0 hours of engineering $5,600
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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-2025-15576 in production — separate from our analysis above.

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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
  • 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