Auth bypass in Jwt Ruby-Jwt
CVE-2026-45363
ruby-jwt is a Ruby implementation of the RFC 7519 OAuth JSON Web Token standard. Prior to 2.10.3 and 3.2.0, JWT.decode(token, '', true, algorithm: 'HS256') accepts an attacker-forged token because OpenSSL::HMAC.digest('SHA256', '', payload) returns a valid digest under an empty key and no empty-key precondition exists in the HMAC algorithm. The same path is reached when a keyfinder block or key_finder: argument returns an empty string, nil, or an array containing nil for an unknown key, affecting HS256, HS384, and HS512 verification through JWT.decode and JWT::EncodedToken#verify_signature!. This issue is fixed in versions 2.10.3 and 3.2.0.
Vulnerability class: Broken Authentication
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.004 (28.7th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 29th percentile — 28.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.004 · change: +0.001
Affected products
- Jwt Ruby-Jwt — versions < 2.10.3, >= 3.0.0, < 3.2.0
Weakness classification (CWE)
References
- github.com/jwt/ruby-jwt/security/advisories/GHSA-c32j-vqhx-rx3x
- github.com/jwt/ruby-jwt/commit/9820020869ad147b941e49d96ab8beba35532964
- github.com/jwt/ruby-jwt/commit/db560b769a07bd9724e77ff505011ac01872106f
- github.com/jwt/ruby-jwt/releases/tag/v2.10.3
- github.com/jwt/ruby-jwt/releases/tag/v3.2.0
- af854a3a-2127-422b-91ae-364da2661108
Frequently asked questions
- What is CVE-2026-45363?
- CVE-2026-45363 is a critical-severity vulnerability in Jwt Ruby-Jwt, classified under Improper Authentication. CVSS score: 9.1/10. Published 2026-07-14.
- How severe is CVE-2026-45363?
- Critical severity. CVSS v3 base score is 9.1 out of 10.