CVE-2026-44351
Deferred
Deferred - Pending Action
BaseFortify
Publication date: 2026-05-13
Last updated on: 2026-05-14
Assigner: GitHub, Inc.
Description
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.
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
Currently, no data is known.
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-287 | When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. |
| CWE-326 | The product stores or transmits sensitive data using an encryption scheme that is theoretically sound, but is not strong enough for the level of protection required. |
| CWE-1391 | The product uses weak credentials (such as a default key or hard-coded password) that can be calculated, derived, reused, or guessed by an attacker. |
Attack-Flow Graph
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