{"id":"GHSA-6vvh-pxr4-25r7","aliases":[],"url":"https://o3.security/vulnerability/GHSA-6vvh-pxr4-25r7","summary":"PHP JWT Framework: Chacha20Poly1305 key-encryption algorithm discards the Poly1305 authentication tag, performing no authentication on decryption","details":"### Impact\n\nThe experimental `Chacha20Poly1305` key-encryption algorithm generates the 16-byte Poly1305 authentication tag during `encryptKey()` but **discards it**: the tag is never written to the header and therefore never reaches the wire. On the receiving side, `decryptKey()` calls `openssl_decrypt('chacha20-poly1305', ...)` **without the tag argument**, which makes OpenSSL skip authentication entirely.\n\nAs a result the AEAD construction is silently degraded to unauthenticated ChaCha20: a tampered encrypted CEK is accepted, and because ChaCha20 is a stream cipher, a single-byte change in the ciphertext propagates as a single-byte change in the recovered CEK with no integrity check (CWE-353 / CWE-347). An attacker on the token path can manipulate the wrapped key without detection.\n\n### Affected configurations\n\nApplications that register `Jose\\Experimental\\KeyEncryption\\Chacha20Poly1305` (package `web-token/jwt-experimental`) as a JWE `alg`.\n\n### Patches\n\n`encryptKey()` now publishes the Poly1305 tag as the base64url `tag` header parameter (and asserts it is 16 bytes). `decryptKey()` requires the `tag` header, validates its length, and passes it to `openssl_decrypt()` so the tag is actually verified, in line with RFC 7539 / RFC 8439. Tampering now results in a decryption failure.\n\n> Note: this changes the wire format of tokens produced with this experimental algorithm (a `tag` header is now emitted and required).\n\n### Workarounds\n\nDo not use the experimental `Chacha20Poly1305` key-encryption algorithm for untrusted input until upgraded.\n\n### References\n\n- RFC 7539 / RFC 8439 (ChaCha20-Poly1305 AEAD)\n- CWE-353: Missing Support for Integrity Check\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**ChaCha20-Poly1305** — le tag d'authentification Poly1305 est désormais publié dans le header au chiffrement et vérifié au déchiffrement (RFC 7539), rétablissant l'intégrité AEAD.\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`.","published":"2026-06-18T21:08:15Z","modified":"2026-06-18T21:15:07.351924462Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Packagist","name":"web-token/jwt-experimental","fixedVersion":null},{"ecosystem":"Packagist","name":"web-token/jwt-library","fixedVersion":"3.4.10"},{"ecosystem":"Packagist","name":"web-token/jwt-library","fixedVersion":"4.0.7"},{"ecosystem":"Packagist","name":"web-token/jwt-library","fixedVersion":"4.1.7"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/web-token/jwt-framework/security/advisories/GHSA-6vvh-pxr4-25r7"},{"type":"WEB","url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/web-token/jwt-library/GHSA-6vvh-pxr4-25r7.yaml"},{"type":"PACKAGE","url":"https://github.com/web-token/jwt-framework"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-06-18T21:15:07.351924462Z"}}