Auth bypass in Formbricks
CVE-2025-59934
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.
Vulnerability class: Broken Authentication
EPSS: 0.080 (94.2th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 9.4 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L.
Affected products
- Formbricks — versions < 4.0.1
Weakness classification (CWE)
Public proof-of-concept exploits
References
- security-advisories@github.com (x_refsource_CONFIRM)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
Frequently asked questions
- What is CVE-2025-59934?
- CVE-2025-59934 is a critical-severity vulnerability in Formbricks, classified under Improper Authentication. CVSS score: 9.4/10. Published 2025-09-26.
- How severe is CVE-2025-59934?
- Critical severity. CVSS v3 base score is 9.4 out of 10.
- Is CVE-2025-59934 known to be exploited?
- 3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.