# CVE-2026-45363

## Summary

- **CVE ID:** CVE-2026-45363
- **Severity:** CRITICAL
- **CVSS Score:** 9.1 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N)
- **CWE:** CWE-287, CWE-326, CWE-1391
- **Published:** Jul 14, 2026
- **Last Modified:** Jul 15, 2026

## Description

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.

## Affected Products

- jwt — ruby-jwt (< 2.10.3)
- jwt — ruby-jwt (>= 3.0.0, < 3.2.0)

## References

- [CNA](https://github.com/jwt/ruby-jwt/security/advisories/GHSA-c32j-vqhx-rx3x)
- [CNA](https://github.com/jwt/ruby-jwt/commit/9820020869ad147b941e49d96ab8beba35532964)
- [CNA](https://github.com/jwt/ruby-jwt/commit/db560b769a07bd9724e77ff505011ac01872106f)
- [CNA](https://github.com/jwt/ruby-jwt/releases/tag/v2.10.3)
- [CNA](https://github.com/jwt/ruby-jwt/releases/tag/v3.2.0)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.24%
- **EPSS Percentile:** 15.3

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._