CVE-2026-41690: Prototype pollution and path traversal in i18next-http-middleware via user-controlled language and namespace parameters
18next-http-middleware is a middleware to be used with Node.js web frameworks like express or Fastify and also for Deno. Versions prior to 3.9.3 allow an unauthenticated HTTP client to pollute Object.prototype in the Node.js process hosting the middleware, via two unvalidated entry points that reach internal object-key writes: getResourcesHandler and missingKeyHandler. This can break authorisation checks (if (user.isAdmin) returning true for any user), cause type-confusion DoS, and depending on downstream code it can be chained into RCE.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-41690?
CVE-2026-41690 has been classified as a critical vulnerability due to its potential for prototype pollution and path traversal.
How do I fix CVE-2026-41690?
To mitigate CVE-2026-41690, upgrade i18next-http-middleware to version 3.9.3 or later.
What software is affected by CVE-2026-41690?
CVE-2026-41690 affects versions of the i18next-http-middleware prior to 3.9.3.
What are the potential impacts of CVE-2026-41690?
The vulnerability may lead to unauthorized access and data manipulation due to prototype pollution and path traversal.
Is CVE-2026-41690 exploitable without authentication?
Yes, CVE-2026-41690 can be exploited by unauthenticated HTTP clients, making it particularly dangerous.