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CVE-2025-27370

• Severity: medium (CVSS 6.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-03-03 · updated 2026-06-17
• Weakness: CWE-305

Description

OpenID Connect Core through 1.0 errata set 2 allows audience injection in certain situations. When the private_key_jwt authentication mechanism is used, a malicious Authorization Server could trick a Client into writing attacker-controlled values into the audience, including token endpoints or issuer identifiers of other Authorization Servers. The malicious Authorization Server could then use these private key JWTs to impersonate the Client.

Affected products

• OpenID Connect: through 1.0 errata set 2

References

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

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