Is CVE-2026-102271 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-102271?

CVE-2026-102271 has a CVSS v3 severity of HIGH (7.4).

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CVE-2026-102271

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.