CVE-2019-6476
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 · uneditedA defect in code added to support QNAME minimization can cause named to exit with an assertion failure if a forwarder returns a referral rather than resolving the query. This affects BIND versions 9.14.0 up to 9.14.6, and 9.15.0 up to 9.15.4.
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 confidenceA denial of service vulnerability in BIND DNS server versions 9.14.0-9.14.6 and 9.15.0-9.15.4. The QNAME minimization feature contains a defect that causes named to exit via assertion failure when a forwarder returns a DNS referral instead of a resolved answer.
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>= 9.14.0, <= 9.14.6>= 9.15.0, <= 9.15.4CVSS 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
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/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 installed BIND versionRun `named -v` or `named -V` to determine the exact version of the BIND named daemonAffected if Version is 9.14.0-9.14.6 or 9.15.0-9.15.4 (older than 9.14.7 or 9.15.5)
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Verify QNAME minimization is enabledSearch named.conf for the directive `qname-minimization` and confirm it is set to `enabled` or `yes`Affected if QNAME minimization is explicitly enabled (it is not enabled by default in affected versions)
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Confirm forwarders are configuredSearch named.conf for a `forwarders` block listing upstream DNS serversAffected if Forwarders are configured and in use (the bug triggers when a forwarder returns a referral instead of a resolved answer)
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Check for recent assertion failure crashesReview named logs and system logs (syslog) for messages containing 'assertion failure' or 'named' process restarts around the time of DNS queriesAffected if Named has crashed with assertion failures while processing queries
Environment is affected if BIND version is 9.14.0-9.14.6 or 9.15.0-9.15.4 AND QNAME minimization is enabled AND forwarders are configured, exposing the server to crashes on DNS referrals
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 BIND to versions 9.14.7/9.15.5 or later. As a temporary workaround, QNAME minimization can be disabled in named.conf until patching is possible.
- Consultation2.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2019-6476 — 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-2019-6476 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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- 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
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