CVE-2026-42353: i18next i18next-HTTP-Middleware

High severity, CVSS 8.2. EPSS: 0.4% chance of exploitation in the next 30 days.

i18next-http-middleware is a middleware to be used with Node.js web frameworks like express or Fastify and also for Deno. Prior to version 3.9.3, i18next-http-middleware passes the user-controlled lng and ns values from getResourcesHandler directly into i18next.services.backendConnector.load(languages, namespaces, …) without any sanitization. Depending on which backend is configured, the unvalidated path segments enable either path traversal or SSRF. This issue has been patched in version 3.9.3.

Affected products

• i18next i18next-HTTP-Middleware: before 3.9.3 (fixed in 3.9.3)

Published 2026-05-08. Last modified 2026-06-17.