i18next i18next-http-backend up to 4.0.3 interpolateUrl lng/ns cross site scripting

Summaryinfo

A vulnerability categorized as problematic has been discovered in i18next i18next-http-backend up to 4.0.3. This vulnerability affects the function interpolateUrl. Such manipulation of the argument lng/ns leads to cross site scripting. This vulnerability is documented as CVE-2026-118258. The attack can be executed remotely. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in i18next i18next-http-backend up to 4.0.3. It has been rated as problematic. Affected by this issue is the function interpolateUrl. The manipulation of the argument lng/ns with an unknown input leads to a cross site scripting vulnerability. Using CWE to declare the problem leads to CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Impacted is integrity. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-118258 since 10/27/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1059.007.

Upgrading to version 4.0.4 eliminates this vulnerability.

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Productinfo

Vendor

• i18next

Name

• i18next-http-backend

Version

• 4.0.0
• 4.0.1
• 4.0.2
• 4.0.3

Website

• Product: https://github.com/i18next/i18next-http-backend/

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