# Denial of Service in uap-core when processing crafted User-Agent strings

Advisory record · `GHSA-cmcx-xhr8-3w9p`

- **Identifiers:** `GHSA-cmcx-xhr8-3w9p` · `CVE-2020-5243`
- **State:** Confirmed
- **Severity:** CVSS 5.7 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-20](https://cwe.mitre.org/data/definitions/20.html) · [CWE-1333](https://cwe.mitre.org/data/definitions/1333.html)
- **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md) · [CWE-20](https://agentprime.io/advisories/tag/cwe-20.md)
- **Published:** 20 Feb 2020
- **Updated:** 8 Jul 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 20 Feb 2020, 23:26 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `uap-core` (npm): affected `<0.7.3`; fixed in `0.7.3`
- `user_agent_parser` (RubyGems): affected `<2.6.0`; fixed in `2.6.0`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 5.7 Medium, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.023, the 83rd percentile, on 9 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the GitHub Advisory Database, published 20 Feb 2020. New records show when each source confirmed them.

## Sources

- [GitHub Advisory Database: GHSA-cmcx-xhr8-3w9p](https://github.com/advisories/GHSA-cmcx-xhr8-3w9p)
- [OSV: GHSA-cmcx-xhr8-3w9p](https://osv.dev/vulnerability/GHSA-cmcx-xhr8-3w9p)
- <https://github.com/ua-parser/uap-core/security/advisories/GHSA-cmcx-xhr8-3w9p>
- <https://github.com/ua-parser/uap-ruby/security/advisories/GHSA-pcqq-5962-hvcw>
- <https://nvd.nist.gov/vuln/detail/CVE-2020-5243>
- <https://github.com/ua-parser/uap-core/commit/0afd61ed85396a3b5316f18bfd1edfaadf8e88e1>
- <https://github.com/rubysec/ruby-advisory-db/blob/master/gems/user_agent_parser/CVE-2020-5243.yml>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-cmcx-xhr8-3w9p>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-cmcx-xhr8-3w9p/>. Everything for agents: <https://agentprime.io/llms.txt>.