CVE-2026-48713
Publiée le 2026-06-15 · Dernière modification le 2026-10-25
Les applications utilisant des versions d'i18next antérieures à la 2.6.6 qui permettent à des utilisateurs non approuvés de déclencher la persistance de clés manquantes sont concernées. Un attaquant non authentifié disposant d'un accès réseau peut envoyer une requête spécialement conçue pour injecter des propriétés dans le prototype de l'objet JavaScript global, ce qui peut entraîner des plantages de l'application, un empoisonnement de la configuration ou le contournement de contrôles de sécurité. Cette attaque est facile à exécuter car elle ne nécessite aucun privilège spécial ni interaction de l'utilisateur.
DÉTAIL DU VECTEUR CVSS
RÉFÉRENCES
Description officielle du NVD (en anglais)
Versions prior to 2.6.6 are vulnerable to prototype pollution via crafted missing-key strings when used to persist missing translation keys (e.g. via i18next-http-middleware's missingKeyHandler exposed to untrusted input). Backend.writeFile() splits each queued missing-key string on the configured keySeparator (default .) before calling the internal setPath() walker. The walker (getLastOfPath in lib/utils.js) did not guard against unsafe segments, so a key like "__proto__.polluted" was split into ["__proto__", "polluted"] and walked straight into Object.prototype, allowing an attacker to write arbitrary properties onto the global object prototype. Depending on the host application, polluted prototype properties may cause crashes, corrupted translation behaviour, configuration poisoning, or bypasses of property-based security checks. Applications are affected only if the missingKeyHandler (or another route that forwards untrusted request bodies to i18next.t(..., { ... }) with saveMissing: true) is reachable by untrusted users and the default behaviour of splitting missing-key strings on keySeparator is in use (i.e. keySeparator is not false). Apps that do not expose missing-key persistence to untrusted input are not directly affected through this attack path. This issue has been fixed in version 2.6.6. If developers using the library are unable to upgrade immediately, they should take the following precautions: do not expose i18next-http-middleware's missingKeyHandler to untrusted users (mount it behind authentication, or remove the route), disable missing-key persistence (saveMissing: false, or no backend.create implementation) when accepting writes from untrusted input, and set keySeparator: false in their i18next options to disable backend key splitting (note: this also disables nested translation keys).