CVE-2018-16853
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 · uneditedSamba from version 4.7.0 has a vulnerability that allows a user in a Samba AD domain to crash the KDC when Samba is built in the non-default MIT Kerberos configuration. With this advisory the Samba Team clarify that the MIT Kerberos build of the Samba AD DC is considered experimental. Therefore the Samba Team will not issue security patches for this configuration. Additionally, Samba 4.7.12, 4.8.7 and 4.9.3 have been issued as security releases to prevent building of the AD DC with MIT Kerberos unless --with-experimental-mit-ad-dc is specified to the configure command.
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 confidenceSamba versions 4.7.0 through 4.7.11, 4.8.0 through 4.8.6, and 4.9.0 through 4.9.2 contain a vulnerability in the MIT Kerberos configuration of the AD DC where an authenticated domain user can cause a denial of service by crashing the KDC 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>= 4.7.0, < 4.7.12>= 4.8.0, < 4.8.7>= 4.9.0, < 4.9.3CVSS 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
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.0/AV:N/AC:H/PR:N/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 checksWork through these to decide whether this CVE applies to you.
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Check Samba versionRun 'samba --version' or check installed package version (e.g., dpkg -l samba, rpm -q samba)Affected if Version is 4.7.0 through 4.7.11, 4.8.0 through 4.8.6, or 4.9.0 through 4.9.2
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Verify Samba is running as AD DCCheck smb.conf for 'server role = active directory domain controller' or check for 'samba' process running as DC (ps aux | grep samba)Affected if Samba is operating as an Active Directory Domain Controller
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Check if MIT Kerberos is enabledReview the Samba build configuration (e.g., check for --with-experimental-mit-ad-dc in build flags) or examine if the KDC is using MIT Kerberos libraries rather than Heimdal. This may require checking build scripts or binary linked libraries (ldd on samba binary)Affected if Samba AD DC is built or configured to use MIT Kerberos instead of the default Heimdal Kerberos
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Confirm KDC service is exposedVerify the KDC service (typically UDP port 88) is listening and accessible on the AD DCAffected if KDC service is running and accessible to authenticated domain users
A user is affected if their Samba version is in the affected range, the server is operating as an AD DC, and MIT Kerberos is enabled in the build or configuration.
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 data4.7.124.8.74.9.3
Ensure Samba AD DC is not built with the experimental MIT Kerberos configuration; upgrade to 4.7.12, 4.8.7, 4.9.3 or later which disables MIT Kerberos AD DC builds by default unless explicitly enabled with --with-experimental-mit-ad-dc.
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2018-16853 — 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-2018-16853 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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