nearform fast-jwt up to 5.0.5 JSON Web Token data authenticity

Summaryinfo

A vulnerability labeled as problematic has been found in nearform fast-jwt up to 5.0.5. This impacts an unknown function of the component JSON Web Token Handler. Executing a manipulation can lead to data authenticity. This vulnerability is registered as CVE-2025-30144. It is possible to launch the attack remotely. No exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability has been found in nearform fast-jwt up to 5.0.5 and classified as problematic. This vulnerability affects an unknown part of the component JSON Web Token Handler. The manipulation with an unknown input leads to a data authenticity vulnerability. The CWE definition for the vulnerability is CWE-345. The product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data. As an impact it is known to affect integrity. CVE summarizes:

fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 5.0.6, the fast-jwt library does not properly validate the iss claim based on the RFC 7519. The iss (issuer) claim validation within the fast-jwt library permits an array of strings as a valid iss value. This design flaw enables a potential attack where a malicious actor crafts a JWT with an iss claim structured as ['https://attacker-domain/', 'https://valid-iss']. Due to the permissive validation, the JWT will be deemed valid. Furthermore, if the application relies on external libraries like get-jwks that do not independently validate the iss claim, the attacker can leverage this vulnerability to forge a JWT that will be accepted by the victim application. Essentially, the attacker can insert their own domain into the iss array, alongside the legitimate issuer, and bypass the intended security checks. This issue is fixed in 5.0.6.

The advisory is shared for download at github.com. This vulnerability was named CVE-2025-30144 since 03/17/2025. The exploitation appears to be difficult. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are neither technical details nor an exploit publicly available.

Upgrading to version 5.0.6 eliminates this vulnerability.

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Productinfo

Vendor

• nearform

Name

• fast-jwt

Version

• 5.0.0
• 5.0.1
• 5.0.2
• 5.0.3
• 5.0.4
• 5.0.5

Website

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

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