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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

3.7 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

EPSS

• CVE-2026-118258: 0.28% estimated exploitation activity in the next 30 days; percentile 20.61 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The URL-segment check added for GHSA-q89c-q3h5-w34g blocks `?`, `#`, `%`, `:`, `/` and `@` in `lng`, but not `&` or `=`, and the checked value is inserted into the URL without encoding. The README documents a multiload loadPath of the form `/locales/resources.json?lng=de+en&ns=ns1+ns2`. With a template like that, an attacker who controls the language value can add or override query parameters on the request the backend sends. By default the language comes from `?lng=`, a cookie or `Accept-Language`. This is the "query-string injection" impact described in GHSA-q89c; only the `?` form was closed. Server side (Express + i18next-http-middleware, default options), `GET /?lng=de%26ns%3Dprivate%26admin%3Dtrue` makes the application request `…?lng=de&ns=private&admin=true&ns=common` from its own translations API.

Details The checks are in `lib/utils.js`. The base check (https://github.com/i18next/i18next-http-backend/blob/v4.0.3/lib/utils.js#L26-L44) rejects: - empty or…

Published by the source

28 Oct 2026, 21:10 UTC

Last modified by the source

28 Oct 2026, 21:30 UTC

Source last checked

29 Oct 2026, 06:00 UTC

1. Revision 2 · amended · 29 Oct 2026

   Amended from osv record GHSA-3cmx-xjww-583x

2. Revision 1 · created · 28 Oct 2026

   Published from ghsa record GHSA-3cmx-xjww-583x

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# Patch Next advisory brief: CVE-2026-118258

Advisory: i18next-http-backend: Query-parameter injection through & and = in lng when loadPath/addPath puts {{lng}} in the query string
IDs: CVE-2026-118258, GHSA-3cmx-xjww-583x
Record: https://patchnext.com/advisories/cve-2026-118258 (revision 2, source checked 29 Oct 2026, 06:00 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 3.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: i18next-http-backend 4.0.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm i18next-http-backend: affected < 4.0.4; fixed in 4.0.4

## Suggested inspection (read-only)
- `npm ls i18next-http-backend --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on i18next-http-backend.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-3cmx-xjww-583x (OSV record GHSA-3cmx-xjww-583x lists affected ranges: npm i18next-http-backend >=0 <4.0.4 (fixed))
- Verified: https://github.com/advisories/GHSA-3cmx-xjww-583x (GitHub-reviewed advisory GHSA-3cmx-xjww-583x lists affected ranges: npm i18next-http-backend >=0 <4.0.4)

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