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FreeBSDOperating system

CVE-2020-7455

MEDIUM · 5.5 CVSS v3.1 Published 2020-05-13
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 FreeBSD 12.1-STABLE before r360973, 12.1-RELEASE before p5, 11.4-STABLE before r360973, 11.4-BETA1 before p1 and 11.3-RELEASE before p9, the FTP packet handler in libalias incorrectly calculates some packet length allowing disclosure of small amounts of kernel (for kernel NAT) or natd process space (for userspace natd).

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

The FTP packet handler in FreeBSD's libalias library incorrectly calculates packet lengths, leading to an out-of-bounds read that discloses small amounts of kernel memory (for kernel NAT) or natd userspace process memory. This information disclosure vulnerability stems from improper bounds checking in the FTP ALG (Application Layer Gateway).

MitigationUpdate FreeBSD systems to version 12.1-STABLE r360973 or later, 12.1-RELEASE p5 or later, 11.4-STABLE r360973 or later, or 11.3-RELEASE p9 or later to obtain the patched libalias implementation.

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= 12.1

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
High
Integrity
None
Availability
None

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/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 checks

Work through these to decide whether this CVE applies to you.

  1. Check FreeBSD base system version
    Run 'uname -a' or 'freebsd-version -u' to identify the installed FreeBSD version
    Affected if The version is 11.3, 11.4, or 12.1 (or any version matching 11.3-RELEASE through 12.1-RELEASE in the affected range)
  2. Verify if natd userspace daemon is running with FTP ALG
    Check running processes for natd: 'ps aux | grep natd' and inspect /etc/natd.conf for 'enable_alias' or 'ftp' directives
    Affected if natd is running with FTP ALG (libalias) enabled
  3. Check if kernel NAT (ipfw nat) with FTP ALG is configured
    Examine /etc/rc.conf for 'natd_enable="YES"' or 'firewall_nat_enable="YES"' and review ipfw rules: 'ipfw -a list' for nat configuration
    Affected if ipfw nat is enabled and FTP traffic passes through the NAT
  4. Identify if libalias kernel module is loaded
    Run 'kldstat | grep libalias' to see if the libalias module is loaded into the kernel
    Affected if libalias module is loaded and handling FTP traffic

The system is affected only if it runs an affected FreeBSD version (11.3, 11.4, or 12.1) AND has FTP ALG (libalias/natd) actively handling FTP traffic through NAT.

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

Update FreeBSD systems to version 12.1-STABLE r360973 or later, 12.1-RELEASE p5 or later, 11.4-STABLE r360973 or later, or 11.3-RELEASE p9 or later to obtain the patched libalias implementation.

Fix this in FreeBSD Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,080
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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-2020-7455 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
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