CVE-2025-30144— Fast-JWT Improperly Validates iss Claims

Fast-JWT Improperly Validates iss Claims

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.

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

对数据真实性的验证不充分

fast-jwt 安全漏洞

fast-jwt是Nearform开源的一个 JSON Web Token 实现。 fast-jwt 5.0.6之前版本存在安全漏洞，该漏洞源于iss声明验证不当，可能导致伪造JWT。

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