CVE-2026-25537
HIGH
GHSA-h395-gr6q-cpjc
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Lifecycle Timeline
4Description
jsonwebtoken is a JWT lib in rust. Prior to version 10.3.0, there is a Type Confusion vulnerability in jsonwebtoken, specifically, in its claim validation logic. When a standard claim (such as nbf or exp) is provided with an incorrect JSON type (Like a String instead of a Number), the library’s internal parsing mechanism marks the claim as “FailedToParse”. Crucially, the validation logic treats this “FailedToParse” state identically to “NotPresent”. This means that if a check is enabled (like: validate_nbf = true), but the claim is not explicitly marked as required in required_spec_claims, the library will skip the validation check entirely for the malformed claim, treating it as if it were not there. This allows attackers to bypass critical time-based security restrictions (like “Not Before” checks) and commit potential authentication and authorization bypasses. This issue has been patched in version 10.3.0.
Analysis
jsonwebtoken prior to version 10.3.0 allows attackers to bypass JWT time-based validation checks through type confusion when standard claims like nbf or exp are provided with incorrect JSON types. The library incorrectly treats malformed claims as absent rather than invalid, enabling bypass of critical security restrictions if validation is enabled but the claim is not explicitly marked as required. …
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Remediation
Within 24 hours: Identify all applications and services using jsonwebtoken library and their current versions. Within 7 days: Apply patch to upgrade jsonwebtoken to version 10.3.0 or later across all affected systems; prioritize production authentication and API gateway services. …
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