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FreeBSDOperating system

CVE-2020-25582

HIGH · 8.7 CVSS v3.1 Published 2021-03-26
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
93/100
Remediation priority · Urgent
Remotely reachable 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
In FreeBSD 12.2-STABLE before r369334, 11.4-STABLE before r369335, 12.2-RELEASE before p4 and 11.4-RELEASE before p8 when a process, such as jexec(8) or killall(1), calls jail_attach(2) to enter a jail, the jailed root can attach to it using ptrace(2) before the current working directory is changed.

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 12.2 and 11.4 before specific patch levels, a TOCTOU (time-of-check-time-of-use) race condition exists in jail_attach(2). When a privileged process like jexec(8) or killall(1) calls jail_attach(2) to enter a jail, a jailed root user can attach to that process using ptrace(2) before the working directory changes, allowing the jailed user to potentially inspect or control processes outside their jail boundary.

MitigationUpgrade FreeBSD to 12.2-STABLE after r369334, 11.4-STABLE after r369335, 12.2-RELEASE p4 or later, or 11.4-RELEASE p8 or later to patch this race condition in jail_attach(2).

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:= 11.4= 12.2

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
Network
Complexity
Low
Privileges
High
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:H/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. Identify FreeBSD version
    Run `uname -r` or `freebsd-version -k` to obtain the running kernel version
    Affected if Version shows 11.4-RELEASE or 12.2-RELEASE without the p4 or p8 patch level respectively, indicating the unpatched release version
  2. Confirm patch revision number
    Check the source revision by running `strings /boot/kernel/kernel | grep -E 'FreeBSD' | head -1` or examine the patch level in `freebsd-version -u` if available
    Affected if The revision number is earlier than r369334 for 12.x branches or r369335 for 11.x branches, indicating the TOCTOU fix is not included
  3. Determine if jails are actively used
    Run `jls` to list running jails on the system
    Affected if Any jails are running, as jail_attach(2) must be invoked by a privileged process like jexec(8) for the race condition to be triggerable
  4. Verify ptrace accessibility from within jails
    Check the security.jail.sysvipc_allowed sysctl or test ptrace(2) capability from inside a jail context
    Affected if Jailed root users have the ability to call ptrace(2), which is required to exploit the race condition before the working directory change completes
  5. Check for privileged jexec or killall usage
    Review system logs or process accounting for invocations of jexec(8) or killall(1) that trigger jail_attach(2)
    Affected if Privileged processes that call jail_attach(2) are being used on the system, creating the window for the TOCTOU race

A system is affected if it runs FreeBSD 11.4 or 12.2 at versions earlier than the p4/p8 patch levels (or source revisions earlier than r369334/r369335) and actively uses jails where privileged processes invoke jail_attach(2) while jailed root users can access ptrace(2).

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

Upgrade FreeBSD to 12.2-STABLE after r369334, 11.4-STABLE after r369335, 12.2-RELEASE p4 or later, or 11.4-RELEASE p8 or later to patch this race condition in jail_attach(2).

Fix this in FreeBSD Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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Scan for this in your stack

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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-2020-25582 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
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  • Version or environment caveats, and links to real fixes
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