What’s Vulnerable › Vulnerabilities

CVE-2026-102271: PyJWT: Public keys in DER form are accepted as HMAC secrets, bypassing the CVE-2022-29217 guard

• Severity: high (CVSS 7.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-09-28 · updated 2026-10-06
• Weakness: CWE-347

Description

PyJWT is a Python implementation of JSON Web Token standards. From 2.4.0 until 2.14.0, PyJWT HMACAlgorithm.prepare_key is affected because asymmetric-key guard relies on textual markers that are absent from DER encoding. This occurs when an application mixes HMAC and asymmetric algorithms and supplies a DER public key as the shared verification key. As a result, PyJWT uses public DER bytes as an HMAC secret. Consequently, an attacker who knows the public key can forge authenticated HMAC tokens. This issue is fixed in version 2.14.0.

Affected products

• jpadilla pyjwt: from 2.4.0 before 2.14.0 — fixed in 2.14.0

How to fix

Upgrade to a fixed version: jpadilla pyjwt 2.14.0. Check the vendor advisory for mitigations.

References

• https://github.com/jpadilla/pyjwt/commit/2798504fa2663364573cf2d1043d8d7fef389499
• https://github.com/jpadilla/pyjwt/releases/tag/2.14.0
• https://github.com/jpadilla/pyjwt/security/advisories/GHSA-p4g4-x82p-q773
• https://github.com/jpadilla/pyjwt/security/advisories/GHSA-p4g4-x82p-q773

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