GHSA-3prj-6hqw-cm82: PHP JWT Library Denial of Service Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-3prj-6hqw-cm82",
  "modified" : "2026-07-15T21:51:04Z",
  "published" : "2026-06-18T21:09:01Z",
  "aliases" : [ ],
  "summary" : "PHP JWT Library: PBES2-HS*+A*KW unwrap accepts an unbounded p2c iteration count, enabling CPU-amplification denial of service",
  "details" : "### Impact\n\nWhen a JWE uses a password-based key-encryption algorithm (`PBES2-HS256+A128KW`, `PBES2-HS384+A192KW`, `PBES2-HS512+A256KW`), `PBES2AESKW::unwrapKey()` reads the `p2c` (PBKDF2 iteration count) parameter directly from the attacker-controlled JOSE header and passes it to `hash_pbkdf2()` with **no upper bound**. The only validation performed (`checkHeaderAdditionalParameters()`) was `is_int($p2c) && $p2c > 0`.\n\nAn unauthenticated attacker can craft a single JWE whose protected header sets a very large `p2c` (e.g. `100_000_000` ≈ 87 s of CPU, or `PHP_INT_MAX`), forcing a worker to spend an arbitrary amount of CPU inside PBKDF2 **before** the key unwrap can even fail. The decrypter swallows the eventual exception, so the attacker pays almost nothing while the server burns CPU. JSON General serialization (multiple recipients) and multi-key JWKSets multiply the cost. This is a classic uncontrolled-resource-consumption (CWE-400) denial of service.\n\n### Affected configurations\n\nApplications that register any `PBES2-HS*+A*KW` algorithm in their decryption `AlgorithmManager`.\n\n### Patches\n\n`PBES2AESKW` now enforces a configurable maximum iteration count (`DEFAULT_MAX_COUNT = 1_000_000`, well above realistic legitimate values which are a few thousand) in `checkHeaderAdditionalParameters()`, before any PBKDF2 computation. The bound is exposed as a constructor argument so operators can tune it.\n\n### Workarounds\n\nBefore upgrading: validate/limit the `p2c` header with a custom header checker, or do not enable PBES2 algorithms for untrusted tokens.\n\n### References\n\n- RFC 7518 §4.8 (PBES2)\n- CWE-400: Uncontrolled Resource Consumption\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**PBES2** — `PBES2AESKW::unwrapKey()` borne désormais le paramètre `p2c` (constante `DEFAULT_MAX_COUNT = 1_000_000`, configurable via le constructeur) avant tout appel à `hash_pbkdf2()`, empêchant l'amplification CPU (DoS).\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:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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-framework"
    },
    "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"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "web-token/jwt-framework"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0"
      }, {
        "fixed" : "4.0.7"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "web-token/jwt-framework"
    },
    "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-3prj-6hqw-cm82"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/web-token/jwt-library/GHSA-3prj-6hqw-cm82.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/web-token/jwt-framework"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/web-token/jwt-framework/releases/tag/3.4.10"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/web-token/jwt-framework/releases/tag/4.0.7"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/web-token/jwt-framework/releases/tag/4.1.7"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400", "CWE-770" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-18T21:09:01Z",
    "nvd_published_at" : null
  }
}