{"id":"GHSA-5739-39v2-5754","summary":"PHP JWT Library: RSA1_5 (RSAES-PKCS1-v1_5) decryption lacks implicit rejection, exposing a Bleichenbacher/Marvin padding oracle","details":"### Impact\n\n`RSACrypt::decryptWithRSA15()` (used by the `RSA1_5` key-encryption algorithm) implements RSAES-PKCS1-v1_5 decryption by inspecting the padding after RSADP and throwing `InvalidArgumentException` as soon as the padding is malformed. It does **not** implement the implicit-rejection countermeasure required by RFC 3447 §7.2.2 / RFC 8017 §7.1.2 (return a deterministic pseudo-random value of the expected length on padding failure and let the downstream step fail uniformly).\n\nFrom a JWE caller this yields a Bleichenbacher/Marvin padding oracle: an attacker submitting adaptively crafted `encrypted_key` values can distinguish (a) padding rejected, (b) padding valid but wrong CEK length, and (c) padding valid and full AEAD executed — even though `JWEDecrypter` returns the same `false` in all cases — because each path performs a measurably different amount of work, amplifiable by enlarging the ciphertext (CWE-208 timing side channel). Enough adaptive queries can recover the wrapped CEK.\n\n### Affected configurations\n\nApplications that register `RSA1_5` in their decryption `AlgorithmManager` and hold an RSA private key.\n\n### Patches\n\nPKCS#1 v1.5 decryption now performs implicit rejection: on invalid padding (or unexpected recovered length) it returns a random CEK of the expected size selected in constant time, so the full content-decryption (AEAD) step always runs and fails uniformly, removing the observable difference between padding-valid and padding-invalid ciphertexts. Users are still strongly encouraged to migrate to `RSA-OAEP`.\n\n### Workarounds\n\nPrefer `RSA-OAEP`/`RSA-OAEP-256`; do not enable `RSA1_5` for untrusted tokens.\n\n### References\n\n- RFC 3447 §7.2.2 / RFC 8017 §7.1.2\n- Bleichenbacher (1998); Marvin attack\n- CWE-208: Observable Timing Discrepancy\n\n## Résolution\n\nUn correctif a été préparé sur une branche dédiée basée sur `3.4.x`, avec des tests anti-régression dédiés (fork privé temporaire de cette advisory, PR #1).\n\n**RSA1_5** — déchiffrement PKCS#1 v1.5 avec *implicit rejection* en temps constant (RFC 3447 §7.2.2) : un padding invalide n'est plus distinguable d'un padding valide, neutralisant l'oracle Bleichenbacher.\n\n**Validation :** `php -l` OK, PHPUnit vert, aucune nouvelle erreur PHPStan introduite (différentiel nul vs `3.4.x`), aucun commentaire ajouté dans le code source. Après merge, cascade prévue `3.4.x → 4.0.x → 4.1.x`.","modified":"2026-08-31T15:00:08.858887291Z","published":"2026-06-18T21:09:56Z","database_specific":{"cwe_ids":["CWE-208","CWE-385"],"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2026-06-18T21:09:56Z","nvd_published_at":null},"references":[{"type":"WEB","url":"https://github.com/web-token/jwt-framework/security/advisories/GHSA-5739-39v2-5754"},{"type":"WEB","url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/web-token/jwt-library/GHSA-5739-39v2-5754.yaml"},{"type":"PACKAGE","url":"https://github.com/web-token/jwt-framework"}],"affected":[{"package":{"name":"web-token/jwt-library","ecosystem":"Packagist","purl":"pkg:composer/web-token/jwt-library"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.4.10"}]}],"versions":["3.3.0","3.3.1","3.3.2","3.3.3","3.3.4","3.3.5","3.4.0","3.4.1","3.4.2","3.4.3","3.4.4","3.4.5","3.4.6","3.4.7","3.4.8","3.4.9"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-5739-39v2-5754/GHSA-5739-39v2-5754.json"}},{"package":{"name":"web-token/jwt-library","ecosystem":"Packagist","purl":"pkg:composer/web-token/jwt-library"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.0.0"},{"fixed":"4.0.7"}]}],"versions":["4.0.0","4.0.1","4.0.2","4.0.3","4.0.4","4.0.5","4.0.6"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-5739-39v2-5754/GHSA-5739-39v2-5754.json"}},{"package":{"name":"web-token/jwt-library","ecosystem":"Packagist","purl":"pkg:composer/web-token/jwt-library"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.1.0"},{"fixed":"4.1.7"}]}],"versions":["4.1.0","4.1.1","4.1.2","4.1.3","4.1.4","4.1.5","4.1.6"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-5739-39v2-5754/GHSA-5739-39v2-5754.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N"}]}