Formbricks up to 4.0.0 JWT signature verification

Summaryinfo

A vulnerability was found in Formbricks up to 4.0.0 and classified as critical. Affected by this issue is some unknown functionality of the component JWT Handler. Such manipulation leads to signature verification. This vulnerability is uniquely identified as CVE-2025-59934. The attack can be launched remotely. No exploit exists. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Formbricks up to 4.0.0. Affected by this issue is an unknown code of the component JWT Handler. The manipulation with an unknown input leads to a signature verification vulnerability. Using CWE to declare the problem leads to CWE-347. The product does not verify, or incorrectly verifies, the cryptographic signature for data. Impacted is confidentiality, integrity, and availability. CVE summarizes:

Formbricks is an open source qualtrics alternative. Prior to version 4.0.1, Formbricks is missing JWT signature verification. This vulnerability stems from a token validation routine that only decodes JWTs (jwt.decode) without verifying their signatures. Both the email verification token login path and the password reset server action use the same validator, which does not check the token’s signature, expiration, issuer, or audience. If an attacker learns the victim’s actual user.id, they can craft an arbitrary JWT with an alg: "none" header and use it to authenticate and reset the victim’s password. This issue has been patched in version 4.0.1.

The advisory is available at github.com. This vulnerability is handled as CVE-2025-59934 since 09/23/2025. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. The technical details are unknown and an exploit is not available.

Upgrading to version 4.0.1 eliminates this vulnerability. Applying the patch eb1349f205189d5b2d4a95ec42245ca98cf68c82 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2025-31394). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Name

• Formbricks

Version

• 4.0

License

• open-source

Website

• Product: https://github.com/formbricks/formbricks/

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If you want to get best quality of vulnerability data, you may have to visit VulDB.

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