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FedoraOperating system · Fedoraproject

CVE-2023-42670

MEDIUM · 6.5 CVSS v3.1 Published 2023-11-03
Fix available
A fix is available. Upgrade to 4.17.12 / 4.18.8 or later.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable 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
A flaw was found in Samba. It is susceptible to a vulnerability where multiple incompatible RPC listeners can be initiated, causing disruptions in the AD DC service. When Samba's RPC server experiences a high load or unresponsiveness, servers intended for non-AD DC purposes (for example, NT4-emulation "classic DCs") can erroneously start and compete for the same unix domain sockets. This issue leads to partial query responses from the AD DC, causing issues such as "The procedure number is out of range" when using tools like Active Directory Users. This flaw allows an attacker to disrupt AD DC services.

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 · moderate confidence

Samba contains a race condition where multiple incompatible RPC listeners can compete for the same unix domain sockets. When the AD DC RPC server experiences high load or becomes unresponsive, NT4-emulation classic DC servers can erroneously start and bind to sockets already in use, causing partial query responses and 'procedure number out of range' errors.

MitigationEnsure proper configuration to prevent NT4-emulation servers from starting when AD DC services are active, and update to patched Samba versions that address this race condition.

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
FedoraOperating system
Affected:= 39
SambaApplication
Affected:< 4.17.12>= 4.18.0, < 4.18.8>= 4.19.0, < 4.19.1

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
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/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 Samba version
    Run 'samba --version' or 'rpm -q samba' to determine the installed version
    Affected if Installed version is < 4.17.12, or >= 4.18.0 and < 4.18.8, or >= 4.19.0 and < 4.19.1, or running on Fedora 39 with vulnerable Samba package
  2. Verify server role configuration
    Examine smb.conf for 'server role' parameter; check for 'server role = classic PDC' or 'server role = classic BDC' to identify NT4-emulation classic DC mode
    Affected if NT4-emulation classic DC mode is enabled alongside AD DC services
  3. Confirm AD DC is active
    Run 'samba -b' or check for 'samba' processes running as domain controller (look for 'samba' service with AD DC functionality)
    Affected if AD DC server is running while NT4-emulation servers may also be active
  4. Inspect for socket conflicts
    Check for unix domain sockets in /tmp/runtime/ or /var/run/samba/ that may be shared between AD DC and NT4-emulation servers
    Affected if Multiple samba processes attempting to bind to the same socket paths
  5. Search for error indicators
    Review Samba logs (typically in /var/log/samba/ or via 'journalctl -u samba') for 'procedure number out of range' errors or partial query responses
    Affected if Logs contain the specific race condition error messages indicating socket conflicts

User is affected if running a vulnerable Samba version (per the version ranges) with both AD DC and NT4-emulation classic DC servers potentially active, evidenced by the race condition causing socket conflicts and 'procedure number out of range' errors in logs.

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 4.17.12 / 4.18.8 / 4.19.1 or later
Fixed in 4.17.124.18.84.19.1
Interim mitigation

Ensure proper configuration to prevent NT4-emulation servers from starting when AD DC services are active, and update to patched Samba versions that address this race condition.

Recommended fix High confidence

Samba 4.17.12, 4.18.8, or 4.19.1 or later (choose based on your current branch)

  1. 1. Check current Samba version: rpm -qa | grep samba or smbd --version
  2. 2. Update package cache: sudo dnf check-update
  3. 3. Upgrade Samba packages to fixed version: sudo dnf update samba
  4. 4. For Fedora 39, ensure update provides Samba >= 4.19.1 (or 4.17.12/4.18.8 depending on branch)
  5. 5. Restart Samba services: sudo systemctl restart smb.service nmb.service winbind.service (or just smb.service for AD DC)
  6. 6. Verify new version is installed: rpm -qa | grep samba
  7. 7. Confirm RPC listeners are functioning correctly: sudo smbstatus or check AD DC health
Caveat Review Samba release notes for the target version for any configuration or feature changes; standard practice to backup smb.conf before upgrading

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

Fix this in Fedora Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,840
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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-2023-42670 in production — separate from our analysis above.

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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