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 a…
Exact source revision recorded 28 Oct 2026 06:07:22 UTC. It does not establish the source's current position. Latest evidence.
euvd · EUVD-2026-30152
Publishedfast-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.
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Original publisher date fields
datePublished: May 13, 2026, 7:12:33 PM
dateUpdated: May 14, 2026, 6:13:32 PM
- Source published
- May 13, 2026, 7:12:33 PM (timezone not stated)
- Source modified
- May 14, 2026, 6:13:32 PM (timezone not stated)
- Observed here
- 28 Oct 2026 06:07:22 UTC
- Source terms
- ENISA EUVD · source terms and attribution apply
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EUVD CVSS 3.1 · 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N