# CVE-2018-0421: Cisco Prime Access Registrar Denial of Service Vulnerability

> Unauthenticated remote attackers can cause a denial of service by sending crafted TCP SYN packets, leading to resource exhaustion and application restarts.

- **Severity:** High 8.6 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 5 Oct 2018
- **Updated:** 26 Nov 2024
- **Also known as:** GHSA-3vp8-x92w-r8qp

## What is CVE-2018-0421?

CVE-2018-0421 is a high-severity denial of service vulnerability in Cisco Prime Access Registrar, published on 5 Oct 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A 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.

Weakness: CWE-772 (Missing Release of Resource after Effective Lifetime), CWE-399

## Which versions are affected by CVE-2018-0421?

It affects 2 products.


Products: Cisco Prime Access Registrar, Cisco Prime Access Registrar Jumpstart.

## How do I fix CVE-2018-0421?

No fix has been published for CVE-2018-0421 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-0421 being exploited?

There is no known exploitation of CVE-2018-0421 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Prime Access Registrar

- [CVE-2022-20626](https://insights.sbomify.com/CVE-2022-20626/): Cisco Prime Access Registrar Appliance Cross-Site Scripting Vulnerability (medium 5.5)
- [CVE-2021-34731](https://insights.sbomify.com/CVE-2021-34731/): Cisco Prime Access Registrar Stored Cross-Site Scripting Vulnerability (medium 4.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-0421 and fix it if it is affected.

What it is: CVE-2018-0421 is a high-severity denial of service vulnerability in Cisco Prime Access Registrar, published on 5 Oct 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2018-0421 in the wild and no public exploit code.

Affected product: Cisco Prime Access Registrar. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2018-0421/ (Markdown: https://insights.sbomify.com/CVE-2018-0421/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-0421
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-0421
- OSV: https://osv.dev/vulnerability/CVE-2018-0421

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-0421/
Summaries are generated and may contain mistakes; the official description above is the record.