Security advisory

{
  "id": "30ccce5919632503615d829b0e942f681c9542b9d6d83c7ed1db3b5df5476c12",
  "url": "https://osv.dev/vulnerability/CVE-2021-46743",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "CVE-2021-46743",
    "summary": "In Firebase PHP-JWT before 6.0.0, an algorithm-confusion issue (e.g., RS256 / HS256) exists via the kid (aka Key ID) header, when multiple types of keys are loaded in a key ring. This allows an attacker to forge tokens that validate under the incorrect key. NOTE: this provides a straightforward way to use the PHP-JWT library unsafely, but might not be considered a vulnerability in the library itself.",
    "evidence": "osv:CVE-2021-46743",
    "products": [],
    "severity": "critical",
    "structured": {
      "id": "CVE-2021-46743",
      "aliases": [
        "CVE-2021-46743",
        "GHSA-8xf4-w7qw-pjjw"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/googleapis/php-jwt",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "0541cba75ab108ef901985e68055a92646c73534"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:google:firebase_php-jwt:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "6.0.0"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v5.5.1",
            "v5.5.0",
            "v5.4.0",
            "v5.3.0",
            "v5.2.1",
            "v5.2.0",
            "v5.1.0",
            "v5.0.0",
            "v4.0.0",
            "v3.0.0",
            "v2.2.0",
            "v2.1.0",
            "v2.0.0",
            "v1.0.0",
            "v0.0.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-46743.json"
          }
        }
      ],
      "modified": "2026-10-20T10:55:12.065820186Z",
      "provider": "osv",
      "references": [
        "https://github.com/firebase/php-jwt/issues/351"
      ],
      "provider_metadata": {}
    },
    "related_cves": [
      {
        "value": "CVE-2021-46743",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 387059,
  "published_at": "2022-03-29T07:15:07.017+00:00"
}