CVE-2025-30144 Fast-JWT Improperly Validates iss Claims
Attackers can bypass JWT issuer validation by crafting tokens with array-based iss claims, allowing forged tokens to be accepted by vulnerable applications.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-30144?
CVE-2025-30144 is a medium-severity authentication bypass vulnerability in nearform fast-jwt, published on 19 Mar 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2025-30144?
2 open source packages ship an affected version, including fast-jwt.
| Package | Affected | Fixed in |
|---|---|---|
fast-jwt npm | All versions | 5.0.6 |
fast-jwt npm | All versions | 5.0.6 |
How do I fix CVE-2025-30144?
Upgrade fast-jwt to 5.0.6 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2025-30144 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-30144 exists.
Public exploit code: 1 proofs of concept on GitHub.
Sources
Also known as GHSA-gm45-q3v2-6cf8.