i18next-http-backend: Query-parameter injection through & and = in lng when loadPath/addPath puts {{lng}} in the query string

[ Why it matters ]Priority signals

• Public proof-of-concept exploit exists (CISA SSVC)

[ Description ]Official description

i18next-http-backend is a backend layer for i18next that loads translation resources in Node.js, browsers, and Deno. Prior to 4.0.4, interpolateUrl inserts unencoded language and namespace values into loadPath or addPath templates without rejecting ampersand (&), equals (=), or semicolon (;) query separators. When a template places lng or ns in the query string and an attacker controls that value, the attacker can add or override parameters on browser or server-side translation requests, potentially exposing other namespaces or tenants or changing backend behavior through the application's network position and credentials. This vulnerability is the result of an incomplete fix for CVE-2026-41691. This issue is fixed in version 4.0.4.

[ Fixes ]Fixes and patches

• i18next-http-backend 4.0.4Fixed version · GitHub Advisories · npm package i18next-http-backend: upgrade to 4.0.4 or later (affected < 4.0.4)

[ Packages ]Affected open-source packages

• i18next-http-backend npmAffected < 4.0.4 · fixed in 4.0.4 · GHSA-3cmx-xjww-583x

[ References ]References

• github.com/i18next/i18next-http-backend/commit/b0eef9efd425055c554787cef7f878de33bbf510
• github.com/i18next/i18next-http-backend/releases/tag/v4.0.4
• github.com/i18next/i18next-http-backend/security/advisories/GHSA-3cmx-xjww-583x