What is CVE-2026-102271?

CVE-2026-102271 is a high-severity vulnerability in Jpadilla Pyjwt, classified under Improper Verification of Cryptographic Signature. CVSS score: 7.4/10. Published 2026-09-28.

How severe is CVE-2026-102271?

High severity. CVSS v3 base score is 7.4 out of 10.

Vulnerability in Jpadilla Pyjwt

CVE-2026-102271

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.

Published 2026-09-28.

CVSS v3 metric

CVSS v3 base score 7.4 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Jpadilla Pyjwt — versions >= 2.4.0, < 2.14.0

Weakness classification (CWE)

CWE-347 — Improper Verification of Cryptographic Signature

References

Frequently asked questions

What is CVE-2026-102271?: CVE-2026-102271 is a high-severity vulnerability in Jpadilla Pyjwt, classified under Improper Verification of Cryptographic Signature. CVSS score: 7.4/10. Published 2026-09-28.
How severe is CVE-2026-102271?: High severity. CVSS v3 base score is 7.4 out of 10.