FreeBSDOperating system
CVE-2002-0820
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 · uneditedFreeBSD kernel 4.6 and earlier closes the file descriptors 0, 1, and 2 after they have already been assigned to /dev/null when the descriptors reference procfs or linprocfs, which could allow local users to reuse the file descriptors in a setuid or setgid program to modify critical data and gain 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 · high confidenceIn FreeBSD kernel 4.6 and earlier, file descriptors 0, 1, and 2 (stdin, stdout, stderr) are incorrectly closed after being assigned to /dev/null when they reference procfs or linprocfs filesystems. This creates a race condition where these standard file descriptors can be reused by local users, potentially allowing them to manipulate file descriptors in setuid or setgid programs to gain elevated privileges.
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
= 4.6CVSS 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
- Authentication
- None
- Confidentiality
- Complete
- Integrity
- Complete
- Availability
- Complete
AV:L/AC:L/Au:N/C:C/I:C/A:C
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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Check FreeBSD kernel versionRun 'uname -r' or 'freebsd-version -k' to obtain the running kernel versionAffected if The version is 4.6 or earlier (e.g., 4.6, 4.5, 4.4, etc.)
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Check if procfs is mountedRun 'mount | grep procfs' to list any mounted procfs filesystemsAffected if procfs is mounted and the kernel version is 4.6 or earlier
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Check if linprocfs is mountedRun 'mount | grep linprocfs' to list any mounted linprocfs filesystemsAffected if linprocfs is mounted and the kernel version is 4.6 or earlier
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Check for procfs/linprocfs in /etc/fstabRun 'grep -E "procfs|linprocfs" /etc/fstab' to see if these filesystems are configured to mount at bootAffected if Either filesystem is configured to mount and the kernel version is 4.6 or earlier
A system is affected if it runs FreeBSD 4.6 or earlier AND has procfs or linprocfs mounted or configured to mount.
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 dataUpgrade FreeBSD systems to a version newer than 4.6 or apply the relevant kernel patch if available. For systems requiring procfs/linprocfs, ensure strict filesystem mounting options and consider migrating to newer FreeBSD releases.
Fix this in FreeBSD
Scoped from the published advisory
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 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 $5,600.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2002-0820 — 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-2002-0820 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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