dbcve.org
FreeBSDOperating system

CVE-2023-5978

HIGH · 7.5 CVSS v3.1 Published 2023-11-08
Fix available
A fix is available. Upgrade to 13.2 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges 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 versions of FreeBSD 13-RELEASE before 13-RELEASE-p5, under certain circumstances the cap_net libcasper(3) service incorrectly validates that updated constraints are strictly subsets of the active constraints.  When only a list of resolvable domain names was specified without setting any other limitations, an application could submit a new list of domains including include entries not previously listed.  This could permit the application to resolve domain names that were previously restricted.

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 cap_net libcasper service in FreeBSD 13-RELEASE before patch 5 fails to validate that updated domain name constraint lists are strict subsets of active constraints. When only a domain list is specified without other limitations, an application can expand the resolvable domains beyond the originally permitted set, bypassing intended restrictions.

MitigationUpgrade to FreeBSD 13-RELEASE-p5 or later, which contains the corrected constraint validation logic in the cap_net libcasper service.

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:>= 13.0, < 13.2= 13.2

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
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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. Check FreeBSD version
    Run 'freebsd-version' or 'uname -r' to determine the installed FreeBSD release version
    Affected if The version is 13.0, 13.1, or 13.2 without being patched to p5 or later (versions 13.0-RELEASE through 13.2-RELEASE before patch 5 are affected)
  2. Identify cap_net libcasper usage
    Search for applications or services that use the cap_net libcasper service by examining running processes and configuration files that reference 'libcasper' or 'cap_net' functionality
    Affected if The system runs any application that utilizes the cap_net libcasper service for DNS resolution with domain restrictions
  3. Review domain constraint configurations
    Examine configuration files or application settings that define DNS domain name constraints through the cap_net service, looking for any 'domain' or 'dns' restriction settings
    Affected if Domain name constraints are defined in the cap_net configuration - the vulnerability allows these constraints to be expanded beyond their original restrictive set
  4. Verify patch level on 13.2 systems
    On systems reporting version 13.2-RELEASE, run 'freebsd-version -k' to check the kernel version and compare against the patched kernel version information
    Affected if The system shows 13.2-RELEASE without the p5 patch applied (the vulnerability exists in unpatched 13.2 releases)

A system is affected if it runs FreeBSD 13.0 through 13.2-RELEASE before patch 5 AND uses the cap_net libcasper service with domain name restrictions that could be expanded beyond their intended limits.

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.

dbcve · scoped
Upgrade available Upgrade to 13.2 or later
Fixed in 13.2
Interim mitigation

Upgrade to FreeBSD 13-RELEASE-p5 or later, which contains the corrected constraint validation logic in the cap_net libcasper service.

Recommended fix High confidence

FreeBSD 13.2-p5 or later (or 13-RELEASE-p5)

  1. 1. Check current FreeBSD version with: uname -a
  2. 2. If running FreeBSD 13.0, 13.1, or 13.2 (prior to p5), update the system to the latest patch level
  3. 3. Run: freebsd-update fetch install
  4. 4. Or fetch and install specific patch: freebsd-update -r 13.2-p5 fetch install
  5. 5. Reboot the system after applying the update
  6. 6. Verify the patch level with: uname -a
Caveat Patch releases are backward-compatible; minimal risk

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in FreeBSD Scoped from the published advisory
  • Consultation2.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
20.0 hours of engineering $3,460
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,536.

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-2023-5978 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