GHSA-3prj-6hqw-cm82
PHP JWT Library: PBES2-HS*+A*KW unwrap accepts an unbounded p2c iteration count, enabling CPU-amplification denial of service
Blast Radius
web-token/jwt-library🐘web-token/jwt-framework🐘web-token/jwt-library🐘web-token/jwt-library🐘web-token/jwt-framework🐘web-token/jwt-frameworkReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Impact
When 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.
An 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.
Affected configurations
Applications that register any PBES2-HS*+A*KW algorithm in their decryption AlgorithmManager.
Patches
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.
Workarounds
Before upgrading: validate/limit the p2c header with a custom header checker, or do not enable PBES2 algorithms for untrusted tokens.
References
- RFC 7518 §4.8 (PBES2)
- CWE-400: Uncontrolled Resource Consumption
Résolution
Un 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).
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).
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | web-token/jwt-library | all versions | 3.4.10 |
| 🐘Packagist | web-token/jwt-framework | all versions | 3.4.10 |
| 🐘Packagist | web-token/jwt-library | ≥ 4.0.0&&< 4.0.7 | 4.0.7 |
| 🐘Packagist | web-token/jwt-library | ≥ 4.1.0&&< 4.1.7 | 4.1.7 |
| 🐘Packagist | web-token/jwt-framework | ≥ 4.0.0&&< 4.0.7 | 4.0.7 |
| 🐘Packagist | web-token/jwt-framework | ≥ 4.1.0&&< 4.1.7 | 4.1.7 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for web-token/jwt-library. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update web-token/jwt-library to 3.4.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-3prj-6hqw-cm82 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-3prj-6hqw-cm82 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-3prj-6hqw-cm82. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-3prj-6hqw-cm82 in your dependencies?
O3 detects GHSA-3prj-6hqw-cm82 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.