Token forgery via RSA public-key misclassification
Published Nov 20, 2023 · Updated Aug 2, 2024
JWT algorithm confusion in Nearform fast-jwt before 3.3.2 allows remote attackers to forge accepted tokens with arbitrary payloads. The publicKeyPemMatcher misses BEGIN RSA PUBLIC KEY, so key detection treats the RSA public key as an HMAC secret and permits HS256. Exploitation requires RS256, that PKCS#1 header, an unspecified verifier algorithm, and the public key; accepted attacker-chosen claims can bypass application authorization.
Summary
What happened
JWT algorithm confusion in Nearform fast-jwt before 3.3.2 allows remote attackers to forge accepted tokens with arbitrary payloads. The publicKeyPemMatcher misses BEGIN RSA PUBLIC KEY, so key detection treats the RSA public key as an HMAC secret and permits HS256. Exploitation requires RS256, that PKCS#1 header, an unspecified verifier algorithm, and the public key; accepted attacker-chosen claims can bypass application authorization.
The record
- CVE
- CVE-2023-48223
- Published
- Nov 20, 2023
- Updated
- Aug 2, 2024
- Vendor
- Nearform
- Product
- fast-jwt
- Classifications
- CWE-20, T1550.001
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Nov 20, 2023CVE publishedPublication date reported by the CVE source.
- Aug 2, 2024Record 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=< 3.3.2
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-c2ff-88x2-x9pg proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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