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Fencer Intel
critical 9.4

CVE-2025-59934 json

Formbricks missing JWT signature verification

published last yr. modified 21d ago also EUVD-2025-31394

cvss
9.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
9.5%
EPSS 9.5% chance of exploitation in 30 days, percentile 95%
public exploits
0
none known

Summary

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.

Patch / fix

Is CVE-2025-59934 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
last yr.

Exploit prediction

9.46% chance of exploitation in the next 30 days, higher than 95% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 9.4 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L

Affected products

  • formbricks formbricks

Classification

Weakness
  • CWE-347 Improper Verification of Cryptographic Signature
  • CWE-345 Insufficient Verification of Data Authenticity
  • CWE-287 Improper Authentication

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.