Authentication bypass via nonconstant-time HMAC signature comparison
Published Feb 8, 2024 · Updated Aug 26, 2024
Authentication bypass in LibJWT 1.15.3 allows remote attackers to forge HMAC-signed JWTs through a timing side channel. The jwt_verify_sha_hmac paths pass computed and supplied signatures to strcmp, whose early-exit comparison leaks prefix-match timing. Exploitation requires repeated measurements against an application exposing HMAC JWT verification; upstream local testing did not reproduce a reliable attack.
Summary
What happened
Authentication bypass in LibJWT 1.15.3 allows remote attackers to forge HMAC-signed JWTs through a timing side channel. The jwt_verify_sha_hmac paths pass computed and supplied signatures to strcmp, whose early-exit comparison leaks prefix-match timing. Exploitation requires repeated measurements against an application exposing HMAC JWT verification; upstream local testing did not reproduce a reliable attack.
The record
- CVE
- CVE-2024-25189
- Published
- Feb 8, 2024
- Updated
- Aug 26, 2024
- Vendor
- LibJWT
- Product
- LibJWT
- Classifications
- CWE-203, T1606
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Feb 8, 2024CVE publishedPublication date reported by the CVE source.
- Aug 26, 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=1.15.3
What conditions does exploitation require?
What is affected?
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.
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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