CVE-2018-16855
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 before version 4.1.8 where a remote attacker sending a DNS query can trigger an out-of-bounds memory read while computing the hash of the query for a packet cache lookup, possibly leading to a crash.
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 confidenceAn out-of-bounds memory read vulnerability exists in PowerDNS Recursor versions before 4.1.8. When processing DNS queries, the Recursor computes a hash for packet cache lookup, and a remote attacker can craft a malicious DNS query to trigger an out-of-bounds read during this hash computation, potentially causing a crash.
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< 4.1.8CVSS 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
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.0/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.
-
Check if PowerDNS Recursor is installedRun 'pdns_recursor --version' or check for the package using your system's package manager (e.g., 'dpkg -l | grep pdns-recursor' on Debian/Ubuntu, 'rpm -qa | grep pdns-recursor' on RHEL/CentOS)Affected if The package is installed and the version number returned is less than 4.1.8 (e.g., 4.1.7, 4.1.6, 4.0.x, etc.)
-
Verify the Recursor service is runningRun 'systemctl status pdns-recursor' or 'service pdns-recursor status' depending on your init system, or check for the pdns_recursor process using 'ps aux | grep pdns_recursor'Affected if The service is active and listening for DNS queries, making it potentially reachable for exploitation
-
Confirm the exact version numberCompare the installed version against the affected range. If running pdns_recursor directly, the output typically shows version in format like '4.1.7' or '4.1.0-rc1'Affected if Any version lower than 4.1.8 is affected, including 4.1.7, 4.1.6, 4.1.0 through 4.1.7, and all 4.0.x and earlier versions
You are affected if PowerDNS Recursor is running with any version lower than 4.1.8 and the service is accessible to process 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 data4.1.8
Upgrade PowerDNS Recursor to version 4.1.8 or later to patch the vulnerability. Consider implementing rate limiting on DNS queries as a temporary defensive measure if immediate upgrade is not feasible.
- Consultation2.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,224.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-16855 — 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-2018-16855 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- 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
- No spam, self-promotion, credentials, or personal data