Vulnerability · Published May 8, 2026 · Assigned by GitHub_M
CVE-2026-41690Prototype pollution and path traversal in i18next-http-middleware via user-controlled language and namespace parameters
High 8.6
In plain English
A high-severity path traversal in i18next-http-middleware from i18next. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 24% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| npm | i18next-http-middleware | 3.9.3 | GHSA-5fgg-jcpf-8jjw |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| i18next | i18next-http-middleware | < 3.9.3 |
Weakness: CWE-22, CWE-1321 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L