Ubuntu LinuxOperating system · Canonical
CVE-2018-20102
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 out-of-bounds read in dns_validate_dns_response in dns.c was discovered in HAProxy through 1.8.14. Due to a missing check when validating DNS responses, remote attackers might be able read the 16 bytes corresponding to an AAAA record from the non-initialized part of the buffer, possibly accessing anything that was left on the stack, or even past the end of the 8193-byte buffer, depending on the value of accepted_payload_size.
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 read vulnerability in HAProxy's dns_validate_dns_response function allows remote attackers to read up to 16 bytes from uninitialized stack memory or past the 8193-byte buffer boundary when processing specially crafted DNS responses. The missing bounds check during DNS response validation enables information disclosure.
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
Ubuntu LinuxOperating system
= 16.04= 18.04= 18.10
Openshift Container PlatformApplication
= 3.11<= 1.8.14CVSS 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
- High
- Integrity
- None
- Availability
- None
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
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 HAProxy installation and versionRun 'haproxy -v' or 'haproxy -V' to get the installed version numberAffected if Version is 1.8.14 or lower (any version <= 1.8.14)
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Check for DNS resolver configuration in HAProxyInspect HAProxy configuration files (commonly /etc/haproxy/haproxy.cfg) for a 'resolvers' section defined in the global or defaults sectionAffected if A 'resolvers' block is defined and referenced by backend servers using 'resolve-opts' or 'resolve-prefer' directives
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Confirm DNS-based service discovery is in useLook for 'option rdns' or 'option reusesess' in backend definitions, or server lines containing 'check inter' with DNS resolution enabledAffected if Backends are configured to perform DNS resolution for health checks or backend server name resolution
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Verify the dns_validate_dns_response code path is reachableIf using HAProxy with a resolvers section, confirm the DNS response handling is active by checking logs or testing DNS response processingAffected if HAProxy is actively processing DNS responses from an upstream DNS server as part of its resolver configuration
You are affected if HAProxy version is 1.8.14 or lower AND the DNS resolver feature is configured and actively processing DNS responses in your environment.
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 HAProxy to version 1.8.14 or later to include the bounds validation fix for DNS response processing.
Fix this in Ubuntu Linux
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,096.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-20102 — 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-2018-20102 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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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