Authentication bypass via array-valued issuer claim
Published Mar 19, 2025 · Updated Mar 19, 2025
Improper issuer validation in Nearform fast-jwt before 5.0.6 allows remote attackers to forge JWTs through an array-valued iss claim. The verifier's iss-claim path accepts an array when any element matches the configured issuer, instead of requiring the RFC-defined string value. Exploitation requires an application that relies on fast-jwt for issuer validation and a key-resolution path such as get-jwks that trusts the attacker-controlled issuer entry; accepted tokens can carry attacker-chosen claims.
Summary
What happened
Improper issuer validation in Nearform fast-jwt before 5.0.6 allows remote attackers to forge JWTs through an array-valued iss claim. The verifier's iss-claim path accepts an array when any element matches the configured issuer, instead of requiring the RFC-defined string value. Exploitation requires an application that relies on fast-jwt for issuer validation and a key-resolution path such as get-jwks that trusts the attacker-controlled issuer entry; accepted tokens can carry attacker-chosen claims.
The record
- CVE
- CVE-2025-30144
- Published
- Mar 19, 2025
- Updated
- Mar 19, 2025
- Vendor
- Nearform
- Product
- fast-jwt
- Classifications
- CWE-290, CWE-345, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 19, 2025CVE publishedPublication date reported by the CVE source.
- Mar 19, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 5.0.6
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- GHSA-gm45-q3v2-6cf8 proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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