{"id":"CVE-2021-46743","aliases":["GHSA-8xf4-w7qw-pjjw"],"url":"https://o3.security/vulnerability/CVE-2021-46743","summary":"Firebase PHP-JWT key/algorithm type confusion","details":"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.","published":"2022-03-29T07:15:07.017Z","modified":"2026-07-08T06:00:42.548721592Z","cvss":{"score":9.1,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":1,"affectedPackages":[{"ecosystem":"Packagist","name":"firebase/php-jwt","fixedVersion":"6.0.0"}],"fix":null,"references":[{"type":"EVIDENCE","url":"https://github.com/firebase/php-jwt/issues/351"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-08T06:00:42.548721592Z"}}