CVE-2019-3806
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 · uneditedAn issue has been found in PowerDNS Recursor versions after 4.1.3 before 4.1.9 where Lua hooks are not properly applied to queries received over TCP in some specific combination of settings, possibly bypassing security policies enforced using Lua.
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 confidenceIn PowerDNS Recursor versions 4.1.4 through 4.1.8, Lua security hooks are not applied to DNS queries received over TCP in certain configuration combinations, allowing those queries to bypass security policies enforced via Lua scripts.
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>= 4.1.4, < 4.1.9CVSS 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
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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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Identify PowerDNS Recursor versionRun 'pdns_recursor --version' or check the installed package version (e.g., 'rpm -q pdns-recursor' or 'dpkg -l pdns-recursor')Affected if The version is 4.1.4, 4.1.5, 4.1.6, 4.1.7, or 4.1.8 (any version from 4.1.4 up to but not including 4.1.9)
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Determine if Lua security hooks are in useInspect the recursor configuration file (typically /etc/powerdns/recursor.conf) for the 'lua-dns-script' directive and review the referenced Lua script for security policy enforcement (e.g., RPZ, query filtering, or access control)Affected if A Lua script is configured via 'lua-dns-script' and contains security policy logic for DNS queries
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Confirm TCP query handling is enabledCheck the recursor configuration for settings that enable TCP downstream queries (such as 'tcp-clients-downstream' or similar TCP-related directives) and verify the service accepts TCP connections on port 53Affected if TCP query handling is enabled in the configuration or the service is listening on TCP port 53 in addition to UDP
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Verify Lua hooks apply to TCPReview the Lua script to confirm it includes hook functions (such as 'prerecordquery', 'preoutquery', or 'ipfilter') that should be applied to both UDP and TCP queries, then test by sending a query over TCP to see if the Lua policy is bypassedAffected if The Lua script contains security enforcement hooks but they are not triggered for TCP queries (the queries bypass the Lua policy)
You are affected if your PowerDNS Recursor version is between 4.1.4 and 4.1.8 inclusive, you use Lua scripts for security policy enforcement, and DNS queries over TCP are accepted and bypass those Lua hooks.
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 data4.1.9
Upgrade PowerDNS Recursor to version 4.1.9 or later. Until then, consider restricting or disabling TCP queries if Lua-based security policies are critical.
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA3.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2019-3806 — 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-2019-3806 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
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