Prime Network RegistrarApplication · Cisco
CVE-2019-1840
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 vulnerability in the DHCPv6 input packet processor of Cisco Prime Network Registrar could allow an unauthenticated, remote attacker to restart the server and cause a denial of service (DoS) condition on the affected system. The vulnerability is due to incomplete user-supplied input validation when a custom extension attempts to change a DHCPv6 packet received by the application. An attacker could exploit this vulnerability by sending malformed DHCPv6 packets to the application. An exploit could allow the attacker to trigger a restart of the service which, if exploited repeatedly, might lead to a DoS condition. This vulnerability can only be exploited if the administrator of the server has previously installed custom extensions that attempt to modify the packet details before the packet has been processed. Note: Although the CVSS score matches a High SIR, this has been lowered to Medium because this condition will only affect an application that has customer-developed extensions that will attempt to modify packet parameters before the packet has been completely sanitized. If packet modification in a custom extension happens after the packet has been sanitized, the application will not be affected by this vulnerability. Software versions prior to 8.3(7) and 9.1(2) are affected.
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 confidenceVulnerability in Cisco Prime Network Registrar's DHCPv6 packet processor allows unauthenticated remote attackers to cause a denial of service by sending malformed DHCPv6 packets. The flaw is due to incomplete input validation when custom extensions attempt to modify packets before sanitization, triggering a server restart.
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
Prime Network RegistrarApplication
< 8.3.7>= 9.0, < 9.1.2CVSS 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.
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Identify Cisco Prime Network Registrar installationLocate the installation directory, typically under /opt/cpnr or C:\Program Files\Cisco Systems\ on Windows. Check for the 'cns-dhcp' or 'cpnr' processes running.Affected if The product is not installed or the version is not in the affected ranges (< 8.3.7 or >= 9.0 and < 9.1.2)
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Determine installed versionRun 'cpnr_version' or 'show version' command from the CPNR bin directory, or check the About section in the web UI.Affected if Version is lower than 8.3.7, or between 9.0.0 and 9.1.1 inclusive
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Verify DHCPv6 service is enabledCheck the DHCPv6 service status via the web UI under DHCPv6 Server settings, or run 'cns-dhcp6 status' from the command line.Affected if DHCPv6 is enabled and running
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Check for custom DHCPv6 extensionsInspect the extensions configuration in the web UI under Extensions or check the extensions directory (typically /opt/cpnr/extensions/ or the configured extensions path in cpnr.conf) for any custom .so or .dll files targeting DHCPv6.Affected if Custom extensions that modify DHCPv6 packets are loaded and active
The environment is affected if Cisco Prime Network Registrar is installed with a vulnerable version AND DHCPv6 is enabled AND custom extensions that modify DHCPv6 packets before sanitization are in use.
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 data8.3.79.1.2
Upgrade to version 8.3(7), 9.1(2), or later. Alternatively, ensure custom extensions modify DHCPv6 packets only after sanitization is complete.
Fix this in Prime Network Registrar
Scoped from the published advisory
- Consultation4.0 h
- Implementation2.0 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-2019-1840 — 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-2019-1840 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.
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- Version or environment caveats, and links to real fixes
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