---
id: CVE-2026-102271
title: PyJWT is a Python implementation of JSON Web Token standards
summary: >-
  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…
severity: high
cvss: 7.4
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N'
cwe:
  - CWE-347
vendor: jpadilla
product: pyjwt
affected:
  - 'pyjwt >= 2.4.0, < 2.14.0'
published: '2026-09-28'
updated: '2026-09-28'
sourceUpdated: '2026-09-28T21:17:15.110'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-102271'
references:
  - url: >-
      https://github.com/jpadilla/pyjwt/commit/2798504fa2663364573cf2d1043d8d7fef389499
    label: security-advisories@github.com
  - url: 'https://github.com/jpadilla/pyjwt/releases/tag/2.14.0'
    label: security-advisories@github.com
  - url: 'https://github.com/jpadilla/pyjwt/security/advisories/GHSA-p4g4-x82p-q773'
    label: security-advisories@github.com
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-28T21:20:54.781Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.