Nearform fast-jwt up to 6.2.x JWT Verification src/decoder.js createVerifier input validation

Summaryinfo

A vulnerability was found in Nearform fast-jwt up to 6.2.x. It has been classified as critical. This affects the function createVerifier of the file src/decoder.js of the component JWT Verification. The manipulation leads to input validation. This vulnerability is uniquely identified as CVE-2026-107723. The attack is possible to be carried out remotely. No exploit exists. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Nearform fast-jwt up to 6.2.x. It has been rated as critical. This issue affects the function createVerifier of the file src/decoder.js of the component JWT Verification. The manipulation with an unknown input leads to a input validation vulnerability. Using CWE to declare the problem leads to CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.3.0, fast-jwt createVerifier accepts a validly signed JWT whose payload is a JSON array because src/decoder.js checks that the payload is an object but does not reject arrays. The claim validator loop then finds no named exp, nbf, iss, aud, sub, jti, or nonce properties and silently skips those configured checks, returning the array as a successfully verified payload. An attacker who can produce or influence a validly signed token may bypass expiry, issuer, audience, subject, revocation, and replay protections. The opt-in requiredClaims option can block missing claims, and signature verification itself is not bypassed. This issue is fixed in version 6.3.0.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-107723 since 10/08/2026. The exploitation is known to be easy. The attack may be initiated remotely. Technical details are known, but no exploit is available.

Upgrading to version 6.3.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-95348). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Vendor

• Nearform

Name

• fast-jwt

Version

• 6.0
• 6.1
• 6.2

Website

• Product: https://github.com/nearform/fast-jwt/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Discussion