---
id: CVE-2026-48523
title: PyJWT is a JSON Web Token implementation in Python
summary: >-
  PyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1,
  there is a verifier-side algorithm allow-list bypass when jwt.decode() or
  jwt.decode_complete() are called with a PyJWK key. The token header alg is
  checked agains…
severity: medium
cvss: 5.4
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N'
cwe:
  - CWE-347
vendor: pyjwt_project
product: pyjwt
affected:
  - 'pyjwt >= 2.9.0, < 2.13.0'
patched:
  - pyjwt 2.13.0
published: '2026-05-28'
updated: '2026-09-16'
sourceUpdated: '2026-09-16T20:16:33.817'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-48523'
references:
  - url: 'https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f'
    label: security-advisories@github.com
  - url: 'https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-48523'
  - url: 'https://github.com/jpadilla/pyjwt'
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/pyjwt/PYSEC-2026-176.yaml
  - url: 'https://github.com/advisories/GHSA-jq35-7prp-9v3f'
tags:
  - nvd
  - osv
  - pip
  - ghsa
epss: 0.00127
epssPercentile: 0.02682
aliases:
  - GHSA-jq35-7prp-9v3f
  - PYSEC-2026-176
ecosystem: pip
ingestedAt: '2026-07-07T15:41:58.720Z'
---

## Overview

PyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1, there is a verifier-side algorithm allow-list bypass when jwt.decode() or jwt.decode_complete() are called with a PyJWK key. The token header alg is checked against the caller-supplied algorithms allow-list, but signature verification is performed with the algorithm bound to the PyJWK object instead of the header algorithm. An attacker who controls a registered JWK/JWKS private key can sign with a disallowed algorithm, advertise an allowed algorithm in the JWT header, and still be accepted. The issue affects the documented PyJWKClient.get_signing_key_from_jwt(...) flow. This vulnerability is fixed in 2.13.0.

## Affected

- `pyjwt >= 2.9.0, < 2.13.0`

## Remediation

Upgrade past the affected range:

- `pyjwt 2.13.0`

## Package advisory (CVE-2026-48523)

Affected packages:

- `pyjwt >= 2.9.0, < 2.13.0`

Patched in:

- `pyjwt 2.13.0`

Source: https://osv.dev/vulnerability/GHSA-jq35-7prp-9v3f