python-jose through 3.5.0 Algorithm Confusion via DER-encoded Public Key as HMAC Secret

{
  "id": "dc903b6fa2b0747966296c4e2508d33d736ef5ef7c89212fed41838154a38e47",
  "url": "https://osv.dev/vulnerability/CVE-2026-85394",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "python-jose through 3.5.0 Algorithm Confusion via DER-encoded Public Key as HMAC Secret",
    "summary": "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.",
    "evidence": "osv:CVE-2026-85394",
    "products": [],
    "severity": "critical",
    "structured": {
      "id": "CVE-2026-85394",
      "aliases": [
        "CVE-2024-33663",
        "CVE-2026-85394",
        "GHSA-3qf3-8w2g-rqmx",
        "GHSA-6c5p-j8vq-pqhj",
        "PYSEC-2024-232",
        "PYSEC-2026-4298"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/mpdavis/python-jose",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "last_affected": "018b310ddb8b50dcfd09a0c152117835a21dd656"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "last_affected": "3.5.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "last_affected": "3.5.0"
                      }
                    ],
                    "source": "DESCRIPTION"
                  }
                ]
              }
            }
          ],
          "versions": [
            "3.5.0",
            "3.4.0",
            "3.3.0",
            "3.2.0",
            "3.1.0",
            "3.0.1",
            "3.0.0",
            "2.0.2",
            "2.0.1",
            "1.4.0",
            "1.3.2",
            "1.3.1",
            "1.3.0",
            "1.2.0",
            "1.1.0",
            "1.0.0",
            "0.7.0",
            "0.6.2",
            "0.6.1",
            "0.6.0",
            "0.5.6",
            "0.5.5",
            "v0.5.4",
            "0.5.3",
            "v0.5.2",
            "v0.5.1",
            "v0.2.0",
            "v0.1.5"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-85394.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:49.314185303Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/85xxx/CVE-2026-85394.json",
        "https://github.com/advisories/GHSA-6c5p-j8vq-pqhj",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-85394",
        "https://www.vulncheck.com/advisories/python-jose-through-3.5.0-algorithm-confusion-via-der-encoded-public-key-as-hmac-secret",
        "https://github.com/mpdavis/python-jose/issues/414",
        "https://github.com/mpdavis/python-jose",
        "https://github.com/mpdavis/python-jose/blob/018b310ddb8b50dcfd09a0c152117835a21dd656/jose/backends/native.py",
        "https://github.com/mpdavis/python-jose/blob/018b310ddb8b50dcfd09a0c152117835a21dd656/jose/utils.py"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-347"
        ],
        "cna_assigner": "VulnCheck",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/85xxx/CVE-2026-85394.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2024-33663",
        "evidence": "/aliases"
      },
      {
        "value": "CVE-2026-85394",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 517532,
  "published_at": "2026-09-03T18:54:26.563+00:00"
}