GHSA-5739-39v2-5754: PHP JWT Library RSA1_5 (RSAES-PKCS1-v1_5) Decryption Lacks Implicit Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-5739-39v2-5754",
  "modified" : "2026-08-31T14:52:45Z",
  "published" : "2026-06-18T21:09:56Z",
  "aliases" : [ ],
  "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`.",
  "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "web-token/jwt-library"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.4.10"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "web-token/jwt-library"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0"
      }, {
        "fixed" : "4.0.7"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "web-token/jwt-library"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.1.0"
      }, {
        "fixed" : "4.1.7"
      } ]
    } ]
  } ],
  "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"
  } ],
  "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
  }
}