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FreeBSDOperating system

CVE-2020-7462

MEDIUM · 5.5 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 →
57/100
Remediation priority · Elevated
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 11.4-PRERELEASE before r360733 and 11.3-RELEASE before p13, improper mbuf handling in the kernel causes a use-after-free bug by sending IPv6 Hop-by-Hop options over the loopback interface. The use-after-free situation may result in unintended kernel behaviour including a kernel panic.

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

FreeBSD kernel use-after-free vulnerability in mbuf handling when processing IPv6 Hop-by-Hop options over the loopback interface. Improper memory management allows freed mbuf structures to be accessed, potentially causing kernel panics.

MitigationApply FreeBSD security patch 11.4-PRERELEASE r360733 or later, or 11.3-RELEASE p13 or later, which corrects the mbuf handling logic for IPv6 Hop-by-Hop options.

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:= 11.3= 11.4

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
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/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 -a` or `freebsd-version -k` to display the installed kernel and userland version
    Affected if The version shown is 11.3 or 11.4 (including point releases like 11.3-RELEASE or 11.4-RELEASE)
  2. Confirm specific release branch
    Run `uname -r` and examine the output format (for example, 11.3-RELEASE-pX or 11.4-RELEASE)
    Affected if The version string begins with 11.3 or 11.4
  3. Verify IPv6 is active on loopback
    Run `ifconfig lo0` and look for inet6 addresses in the output
    Affected if IPv6 is enabled on the loopback interface (inet6 ::1 or fe80::1 addresses present)
  4. Check kernel patch level on 11.3
    If running 11.3, run `sysctl kern.osreldate` and compare to the patched release (11.3-RELEASE-p13 or newer)
    Affected if Running 11.3-RELEASE-p12 or earlier without the security patch

The system is affected if it runs FreeBSD 11.3 or 11.4, has IPv6 enabled on loopback (default), and lacks the patch from r360733 or later (11.3-RELEASEp13 or 11.4-PRERELEASE).

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 FreeBSD security patch 11.4-PRERELEASE r360733 or later, or 11.3-RELEASE p13 or later, which corrects the mbuf handling logic for IPv6 Hop-by-Hop options.

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
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Scan for this in your stack

Free · runs locally
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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-2020-7462 in production — separate from our analysis above.

No notes yet

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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