---
id: CVE-2024-33663
aliases:
  - GHSA-3qf3-8w2g-rqmx
  - CVE-2026-85394
  - GHSA-6c5p-j8vq-pqhj
  - PYSEC-2024-232
  - PYSEC-2026-4298
title: python-jose algorithm confusion guard bypassed by DER-encoded public keys
summary: python-jose algorithm confusion guard bypassed by DER-encoded public keys
severity: critical
cvss: 9.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'
vendor: python-jose
product: python-jose
ecosystem: pip
affected:
  - python-jose <= 3.5.0
patched:
  - python-jose 3.4.0
published: '2026-09-03'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T14:56:01.261338787Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-3qf3-8w2g-rqmx'
references:
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-85394'
  - url: 'https://github.com/mpdavis/python-jose/issues/414'
  - url: 'https://github.com/advisories/GHSA-6c5p-j8vq-pqhj'
  - url: 'https://github.com/mpdavis/python-jose'
  - url: >-
      https://github.com/mpdavis/python-jose/blob/018b310ddb8b50dcfd09a0c152117835a21dd656/jose/backends/native.py
  - url: >-
      https://github.com/mpdavis/python-jose/blob/018b310ddb8b50dcfd09a0c152117835a21dd656/jose/utils.py
  - url: >-
      https://www.vulncheck.com/advisories/python-jose-through-3.5.0-algorithm-confusion-via-der-encoded-public-key-as-hmac-secret
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2024-33663'
  - url: 'https://github.com/mpdavis/python-jose/issues/346'
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/python-jose/PYSEC-2024-232.yaml
  - url: >-
      https://www.vicarius.io/vsociety/posts/algorithm-confusion-in-python-jose-cve-2024-33663
  - url: 'https://pypi.org/project/python-jose'
  - url: 'https://github.com/advisories/GHSA-3qf3-8w2g-rqmx'
tags:
  - osv
  - pip
epss: 0.00307
epssPercentile: 0.234
ingestedAt: '2026-09-04T19:32:57.482Z'
---

## Overview

python-jose through 3.5.0 fails to properly validate asymmetric keys in HMAC initialization, accepting DER-encoded public keys that lack PEM armor or SSH prefixes. Attackers holding the service's public key can forge HS256 tokens that pass verification when algorithms are not explicitly restricted. This is an incomplete fix for CVE-2024-33663.

## Affected packages

- `python-jose <= 3.5.0`

## Remediation

Refer to the advisory for the patched release.