Prime Access RegistrarApplication · Cisco
CVE-2018-0421
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 TCP connection management in Cisco Prime Access Registrar could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition when the application unexpectedly restarts. The vulnerability is due to incorrect handling of incoming TCP SYN packets to specific listening ports. The improper handling of the TCP SYN packets could cause a system file description to be allocated and not freed. An attacker could exploit this vulnerability by sending a crafted stream of TCP SYN packets to the application. A successful exploit could allow the attacker to cause the application to eventually restart if a file description cannot be obtained.
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 confidenceA denial of service vulnerability exists in Cisco Prime Access Registrar's TCP connection management where incoming TCP SYN packets to specific listening ports cause file descriptors to be allocated but not properly freed. Repeated TCP SYN packet injection exhausts available file descriptors, causing the application to restart when it can no longer allocate resources.
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 Access RegistrarApplication
>= 7.3, < 7.3.0.4>= 8.0, < 8.0.1.1
Prime Access Registrar JumpstartApplication
>= 7.3, < 7.3.0.4>= 8.0, < 8.0.1.1CVSS 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
- Changed
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/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 installed product and versionLocate the Cisco Prime Access Registrar installation and retrieve its version number (commonly via CLI command 'show version' or checking installed package details)Affected if Version is 7.3.x where x < 4, or version 8.0.x where x < 2 (i.e., < 7.3.0.4 or < 8.0.1.1)
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Confirm product variantDetermine whether the installation is Cisco Prime Access Registrar or Prime Access Registrar Jumpstart, as both are affectedAffected if Either variant is present with a version in the affected ranges
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Identify TCP listening portsReview the service configuration or run network diagnostics to list TCP ports on which the application is listening (e.g., using 'netstat -an' or checking configuration files for port definitions)Affected if The application has TCP ports open and listening, as the vulnerability triggers via incoming TCP SYN packets to these ports
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Check for symptom artifactsIf the system has been operational, examine system logs or application logs for errors indicating file descriptor exhaustion or unexpected restartsAffected if Logs show file descriptor exhaustion errors, 'too many open files' warnings, or unexplained service restarts correlating with TCP activity
The environment is affected if Cisco Prime Access Registrar (or Jumpstart) version falls within 7.3 through 7.3.0.3 or 8.0 through 8.0.1.0, and the service has TCP listening ports exposed.
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 data7.3.0.48.0.1.1
Apply the vendor patch when released by Cisco. Prior to patch availability, consider implementing network-level controls such as rate limiting or firewall rules on affected listening ports to reduce exposure to unauthenticated TCP SYN floods.
Fix this in Prime Access Registrar
Scoped from the published advisory
- Consultation4.0 h
- Implementation8.0 h
- Testing12.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,616.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-0421 — 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-2018-0421 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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