fast-jwt: Empty HMAC secret accepted via async key resolver - JWT auth bypass
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
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| nearform | fast-jwt | affected |
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| Nearform | Fast-jwt |
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| Source | ID | Title |
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Github GHSA |
GHSA-gmvf-9v4p-v8jc | fast-jwt: JWT auth bypass due to empty HMAC secret accepted by async key resolver |
No CVSS v4.0
No CVSS v3.0
No CVSS v2
This CVE is not in the KEV list.
Exploit prediction score: < 1% (0.250% probability within 30 days)
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| Metrics |
ssvc
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| First Time appeared |
Nearform
Nearform fast-jwt |
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| Vendors & Products |
Nearform
Nearform fast-jwt |
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| Description | fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.2.4, a critical authentication-bypass vulnerability in fast-jwt's async key-resolver flow allows any unauthenticated attacker to forge arbitrary JWTs that are accepted as authentic. When the application's key resolver returns an empty string (''), for example via the common keys[decoded.header.kid] || '' JWKS-style fallback, fast-jwt converts it to a zero-length Buffer, hands it to crypto.createSecretKey, derives allowedAlgorithms = ['HS256','HS384','HS512'] from it, and then verifies the token's signature against an empty-key HMAC. The attacker simply computes HMAC-SHA256(key='', input='${header}.${payload}'), which Node accepts without complaint — and the verifier returns the attacker-chosen payload (sub, admin, scopes, etc.) as authentic. This vulnerability is fixed in 6.2.4. | |
| Title | fast-jwt: Empty HMAC secret accepted via async key resolver - JWT auth bypass | |
| Weaknesses | CWE-1391 CWE-287 CWE-326 |
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| References |
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| Metrics |
cvssV3_1
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