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CVE-2026-45363— `jwt` (Ruby gem) - empty-key HMAC bypass

Quick assessment

Affected
jwt ruby-jwt
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

JSON Web Token jwt是JSON Web Token组织开源的一个Ruby库。 JSON Web Token JWT 2.10.3之前版本和3.0.0版本至3.2.0之前版本存在安全漏洞，该漏洞源于HMAC算法中空密钥检查缺失，可能导致攻击者伪造令牌绕过身份验证。

CVSS 9.1 · Critical EPSS 0.36% · P29

Possible ATT&CK Techniques 1 AI

T1556 · Modify Authentication Process

Affected Version Matrix 2

VendorProduct Version RangeStatus
jwt ruby-jwt < 2.10.3 affected
>= 3.0.0, < 3.2.0 affected
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I. Basic Information for CVE-2026-45363

Vulnerability Information
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Vulnerability Title
`jwt` (Ruby gem) - empty-key HMAC bypass
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
认证机制不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
JSON Web Token JWT 信任管理问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
JSON Web Token jwt是JSON Web Token组织开源的一个Ruby库。 JSON Web Token JWT 2.10.3之前版本和3.0.0版本至3.2.0之前版本存在安全漏洞，该漏洞源于HMAC算法中空密钥检查缺失，可能导致攻击者伪造令牌绕过身份验证。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
jwt ruby-jwt < 2.10.3 -

II. Public POCs for CVE-2026-45363

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 7056 chars
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III. Intelligence Information for CVE-2026-45363

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Patches & Fixes for CVE-2026-45363 (3)

Vendor Advisories for CVE-2026-45363 (1)

Other References for CVE-2026-45363 (1)

IV. Related Vulnerabilities

Same vendor: jwt
Same weakness: CWE-287

V. Comments for CVE-2026-45363

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