High [CVE-2026-45363] Authentication bypass due to empty key in HMAC verification
This high-severity Red Hat Linux advisory covers CVE-2026-45363 affecting Red Hat Satellite 6.
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Summary
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.
A remote attacker can exploit this vulnerability by crafting a malicious token that is accepted due to an empty key being used in the HMAC (Hash-based Message Authentication Code) digest calculation during token verification.
This allows the attacker to bypass authentication and integrity checks, potentially leading to unauthorized access or data manipulation. Red Hat severity: Important — CVSS 7.4 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N).
Weakness: CWE-347. Affected Red Hat products: Red Hat Satellite 6.
Red Hat lists Red Hat Hardened Images as not affected. Red Hat does not currently list a fixing RHSA for this CVE.
- < 2.10.3
- < 3.2.0
Official advisory · high-confidence parse· fetched 5 days ago·verify at source
- 2.10.3
- 3.2.0
Official advisory · high-confidence parse· fetched 5 days ago·verify at source
Mitigation
Upgrade to a fixed release: 2.10.3, 3.2.0. That is the remediation for this advisory.
The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.
Official advisory · high-confidence parse· fetched 5 days ago·verify at source
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