fast-jwt: createVerifier accepts unsigned JWTs when key is '' or null and algorithms is explicitly set

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-107720
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-08 22:17:28 UTC
Updated2026-10-09 15:17:08 UTC
Descriptionfast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.3.1, fast-jwt createVerifier accepts an unsigned JWT when key is an empty string or null and algorithms is a non-empty allowlist. Falsy synchronous keys bypass prepareKeyOrSecret, allowedAlgorithms remains active, hasKey is false, and the empty signature avoids the verifySignature gate. An attacker can therefore submit a token containing arbitrary claims without possessing a signing key, resulting in authentication or authorization bypass. Claim validators still run, and non-empty keys, an empty key without algorithms, and the async key resolver path do not have this behavior. This issue is fixed in version 6.3.1.

Risk And Classification

Primary CVSS: v3.1 7.4 HIGH from [email protected]

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Problem Types: CWE-20 | CWE-347 | CWE-20 CWE-20: Improper Input Validation | CWE-347 CWE-347: Improper Verification of Cryptographic Signature

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.4HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
3.1CNADECLARED7.4HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Nearform Fast-jwt affected < 6.3.1 Not specified

References

ReferenceSourceLinkTags
github.com/nearform/fast-jwt/security/advisories/GHSA-8wpc-h4q6-8fxv 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
github.com/nearform/fast-jwt/commit/e22a151e83bf6d5e54e281216982d204d566... [email protected] github.com
github.com/nearform/fast-jwt/releases/tag/v6.3.1 [email protected] github.com
github.com/nearform/fast-jwt/pull/649 [email protected] github.com
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