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CVE-2026-120459— python-jose through 3.5.0 Authentication Bypass via Empty HMAC Key

Quick assessment

Affected
mpdavis python-jose
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

python-jose 3.5.0 及更早版本存在身份验证绕过漏洞：由于 HMACKey 和 CryptographyHMACKey 允许使用零长度的 HMAC 密钥，未经验证的攻击者可伪造 JWT。当应用程序的 HS256/HS384/HS512 验证密钥解析为空（例如 k 字段为空的 oct JWK）时，攻击者可生成包含任意声明的令牌，而 jwt.decode 仍会接受这些令牌。

CVSS 7.4 · High
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I. Basic Information for CVE-2026-120459

Vulnerability Information
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Vulnerability Title
python-jose through 3.5.0 Authentication Bypass via Empty HMAC Key
Source: CVE Program / CVE List V5
Vulnerability Description
python-jose through 3.5.0 contains an authentication bypass vulnerability that allows unauthenticated attackers to forge JWTs because HMACKey and CryptographyHMACKey accept zero-length HMAC secrets. When an application's HS256/HS384/HS512 verification key resolves to empty, such as an oct JWK with empty k, attackers can forge tokens with arbitrary claims that jwt.decode accepts.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
密码学签名的验证不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
mpdavis python-jose 0 ~ 3.5.0 -

II. Public POCs for CVE-2026-120459

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III. Intelligence Information for CVE-2026-120459

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Other References for CVE-2026-120459 (4)

IV. Related Vulnerabilities

Same product: python-jose
Same vendor: mpdavis
Same weakness: CWE-347