FreeBSDOperating system
CVE-2020-25578
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 · uneditedIn FreeBSD 12.2-STABLE before r368969, 11.4-STABLE before r369047, 12.2-RELEASE before p3, 12.1-RELEASE before p13 and 11.4-RELEASE before p7 several file systems were not properly initializing the d_off field of the dirent structures returned by VOP_READDIR. In particular, tmpfs(5), smbfs(5), autofs(5) and mqueuefs(5) were failing to do so. As a result, eight uninitialized kernel stack bytes may be leaked to userspace by these file systems.
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 confidenceMultiple FreeBSD file systems (tmpfs, smbfs, autofs, mqueuefs) fail to initialize the d_off field in dirent structures when implementing VOP_READDIR, causing 8 bytes of uninitialized kernel stack data to leak to userspace.
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
= 11.4= 12.1= 12.2CVSS 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
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/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 checksWork through these to decide whether this CVE applies to you.
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Identify the FreeBSD versionRun 'uname -r' or check /usr/src/sys/conf/newvers.sh for the version numberAffected if The version is 11.4, 12.1, or 12.2 without the respective patches (11.4-p7, 12.1-p13, 12.2-p3)
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Determine if vulnerable file systems are in useRun 'mount | grep -E "(tmpfs|smbfs|autofs|mqueuefs)"' to list mounted instances of affected file systemsAffected if Any of these file system types are actively mounted on the system
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Check for tmpfs mountsExecute 'df -t tmpfs' or 'mount -t tmpfs' to enumerate tmpfs file systemsAffected if tmpfs is mounted and the kernel version is unpatched
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Check for smbfs mountsRun 'mount | grep smbfs' to find smbfs mountsAffected if smbfs is mounted and the kernel version is unpatched
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Check for autofs mountsRun 'mount -t autofs' or check /etc/auto_master for autofs configurationAffected if autofs is active and the kernel version is unpatched
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Check for mqueuefs mountsRun 'mount | grep mqueue' to check for mqueuefs mountsAffected if mqueuefs is mounted and the kernel version is unpatched
The system is affected if it runs unpatched FreeBSD 11.4, 12.1, or 12.2 AND has any of tmpfs, smbfs, autofs, or mqueuefs file systems mounted or in use.
Generated from the published advisory. Verify against your own configuration.
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 dataApply FreeBSD security patches (12.2-p3, 12.1-p13, 11.4-p7) or upgrade to stable versions after r368969 (12.2) or r369047 (11.4), then reboot the system.
Fix this in FreeBSD
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,648.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-25578 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-25578 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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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.
- 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
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