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CVE-2026-85394— python-jose through 3.5.0 Algorithm Confusion via DER-encoded Public Key as HMAC Secret

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.

Michael Davis python-jose是Michael Davis个人开发者开源的一个 Python 中的 JOSE 实现。 Michael Davis python-jose 3.5.0及之前版本存在加密问题漏洞，该漏洞源于HMAC初始化过程中未正确验证非对称密钥，接受缺少PEM装甲或SSH前缀的DER编码公钥，可能导致持有服务公钥的攻击者在算法未明确限制时伪造通过验证的HS256令牌。

CVSS 9.1 · Critical EPSS 0.22% · P13

Affected Version Matrix 1

VendorProduct Version RangeStatus
mpdavis python-jose ≤ 3.5.0 affected
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I. Basic Information for CVE-2026-85394

Vulnerability Information
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Vulnerability Title
python-jose through 3.5.0 Algorithm Confusion via DER-encoded Public Key as HMAC Secret
Source: CVE Program / CVE List V5
Vulnerability Description
python-jose through 3.5.0 fails to properly validate asymmetric keys in HMAC initialization, accepting DER-encoded public keys that lack PEM armor or SSH prefixes. Attackers holding the service's public key can forge HS256 tokens that pass verification when algorithms are not explicitly restricted. This is an incomplete fix for CVE-2024-33663.
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
密码学签名的验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Michael Davis python-jose 加密问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Michael Davis python-jose是Michael Davis个人开发者开源的一个 Python 中的 JOSE 实现。 Michael Davis python-jose 3.5.0及之前版本存在加密问题漏洞，该漏洞源于HMAC初始化过程中未正确验证非对称密钥，接受缺少PEM装甲或SSH前缀的DER编码公钥，可能导致持有服务公钥的攻击者在算法未明确限制时伪造通过验证的HS256令牌。
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
mpdavis python-jose 0 ~ 3.5.0 -

II. Public POCs for CVE-2026-85394

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III. Intelligence Information for CVE-2026-85394

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Patches & Fixes for CVE-2026-85394 (1)

Vendor Advisories for CVE-2026-85394 (3)

Other References for CVE-2026-85394 (1)

IV. Related Vulnerabilities

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