CVE-2014-0239
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 · uneditedThe internal DNS server in Samba 4.x before 4.0.18 does not check the QR field in the header section of an incoming DNS message before sending a response, which allows remote attackers to cause a denial of service (CPU and bandwidth consumption) via a forged response packet that triggers a communication loop, a related issue to CVE-1999-0103.
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 confidenceThe internal DNS server in Samba 4.x before 4.0.18 fails to validate the QR (Query/Response) bit in DNS message headers before sending responses. An attacker can send a forged DNS response packet with QR set to response that tricks the server into repeatedly responding, creating a communication loop that exhausts CPU and bandwidth resources.
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>= 4.0.0, < 4.0.18>= 4.1.0, < 4.1.8CVSS 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
- Authentication
- None
- Confidentiality
- None
- Integrity
- None
- Availability
- Partial
AV:N/AC:L/Au:N/C:N/I:N/A:P
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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Identify Samba versionRun 'samba --version' or 'smbd --version' to get the installed Samba version. On RPM-based systems use 'rpm -q samba', on Debian-based use 'dpkg -l samba'.Affected if The version is 4.0.0 through 4.0.17, or 4.1.0 through 4.1.7 (versions below 4.0.18 and 4.1.8).
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Locate Samba configuration fileFind smb.conf typically at /etc/samba/smb.conf or /etc/smb.conf. Check with 'testparm -s' which shows the parsed configuration.Affected if Configuration file exists and the system uses Samba as a domain controller with DNS services.
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Verify DNS backend typeIn smb.conf, look for the 'dns update method' parameter or check for 'server services' + 'dns' in the configuration. Also check for 'include = /etc/samba/dns_update_list' or similar DNS-related entries.Affected if The system uses 'samba_internal' as the DNS backend or has DNS update functionality enabled, indicating the internal DNS server is active.
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Confirm DNS service is runningCheck if the Samba DNS service is active: on systemd systems run 'systemctl status samba-ad-dc' or 'systemctl status named' if using BIND. On SysV init, use 'service samba status'. Also check for listening on port 53 with 'netstat -tulpn | grep :53'.Affected if The internal DNS server (samba_ad_dc or named with BIND_DLZ) is running and accepting DNS queries on port 53.
The system is affected if it runs Samba 4.0.0-4.0.17 or 4.1.0-4.1.7 with the internal DNS server (samba_internal) enabled and actively handling DNS queries.
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 data4.0.184.1.8
Upgrade to Samba 4.0.18 or later to obtain the patch that validates the QR field. Alternatively, implement network-level filtering to block spoofed DNS responses from untrusted sources.
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2014-0239 — 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-2014-0239 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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- Version or environment caveats, and links to real fixes
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