CVE-2016-0771
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 4.1.23, 4.2.x before 4.2.9, 4.3.x before 4.3.6, and 4.4.x before 4.4.0rc4, when an AD DC is configured, allows remote authenticated users to cause a denial of service (out-of-bounds read) or possibly obtain sensitive information from process memory by uploading a crafted DNS TXT record.
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 4.1.23, 4.2.9, 4.3.6, 4.4.0rc4) contains an out-of-bounds read vulnerability when configured as an AD DC. Authenticated remote users can exploit this by uploading a crafted DNS TXT record, causing denial of service or potentially reading sensitive data from process memory.
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= 4.0.1= 4.0.2= 4.0.3= 4.0.4= 4.0.5= 4.0.6= 4.0.7= 4.0.8= 4.0.9= 4.0.10= 4.0.11CVSS 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
- High
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- None
- Availability
- High
CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:L/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 checksWork through these to decide whether this CVE applies to you.
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Check installed Samba versionRun 'smbd --version' or 'samba --version' to obtain the exact version numberAffected if Version is 4.0.0 through 4.0.11, or 4.1.0-4.1.22, 4.2.0-4.2.8, 4.3.0-4.3.5, or 4.4.0-4.4.0rc3 (versions before the fixes at 4.1.23, 4.2.9, 4.3.6, 4.4.0rc4)
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Verify Samba is configured as an Active Directory Domain ControllerExamine the 'server role' parameter in /etc/samba/smb.conf; look for 'server role = active directory domain controller'Affected if The 'server role' is set to 'active directory domain controller' (AD DC mode)
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Confirm Samba's internal DNS server is in useCheck smb.conf for the 'dns internal' parameter or look for 'dns forwarder' configuration; absence of an external forwarder typically means internal DNS is activeAffected if Samba's internal DNS server is enabled (not using an external DNS server)
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Verify DNS update functionality is accessibleInspect smb.conf for 'allow dns updates' setting; by default this may be set to 'secure' or 'yes', allowing authenticated users to update DNS recordsAffected if DNS updates are permitted (allow dns updates is not set to 'disabled')
A system is affected if it runs a vulnerable Samba 4.x version (4.0.0-4.0.11 per the provided list, or 4.1-4.3.x/4.4.0rc3 per the fixed versions) AND is configured as an AD DC using Samba's internal DNS server with DNS updates enabled.
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 dataUpgrade Samba to version 4.1.23, 4.2.9, 4.3.6, 4.4.0rc4 or later. If immediate patching is not feasible, restrict DNS update permissions to only essential authenticated users or consider using external DNS servers instead of Samba's internal DNS server.
- Consultation3.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2016-0771 — 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-2016-0771 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
- No weaponised exploit code, or anything meant to cause harm
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