CVE-2019-11331
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 · uneditedNetwork Time Protocol (NTP), as specified in RFC 5905, uses port 123 even for modes where a fixed port number is not required, which makes it easier for remote attackers to conduct off-path attacks.
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 confidenceNTP uses port 123 even for modes where a fixed port is not required, which exposes the protocol to off-path attacks where attackers can inject or manipulate NTP traffic without needing to intercept direct communication between client and server.
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 dataall versionsCVSS 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:3.0/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 if NTP daemon is runningRun command: netstat -tulpn | grep 123 or ss -tulpn | grep 123 to see if port 123 is listeningAffected if NTP daemon is listening on UDP port 123 and no authentication is configured
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Check NTP daemon implementation and versionRun command: ntpd --version, chronyd --version, or ntpq -c version to identify the NTP software and its versionAffected if Any NTP implementation is running - all versions are affected by this vulnerability
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Verify if NTS (NTP Security Extensions) is enabledFor ntpd: check ntp.conf for 'nts' directives or run ntpq -c assoc to check for NTS-enabled associations. For chrony: check chrony.conf for 'nts' directive or run chronyc tracking to check NTS statusAffected if NTS is not enabled - the server is vulnerable to off-path injection attacks
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Check if symmetric key authentication is configuredInspect ntp.conf or chrony.conf for 'trustedkey' or 'key' directives, and verify the presence of keys file referenced in the configurationAffected if No symmetric key authentication is configured - NTP traffic can be manipulated by off-path attackers
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Verify NTP client/server mode exposureConfirm the system is operating as an NTP client or server (not just polling external servers) by checking ntp.conf for 'server' or 'pool' directives (client) or 'allow' directives (server)Affected if System is configured as an NTP client or server using port 123 without cryptographic authentication
If NTP is running on port 123 without NTS or symmetric key authentication enabled, the system is vulnerable to off-path injection attacks as described in CVE-2019-11331.
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 dataEnable NTP Security Extensions (NTS) or configure symmetric key authentication on NTP servers to cryptographically verify the authenticity of NTP responses and prevent injection attacks.
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-11331 — 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-2019-11331 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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