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High, CVSS 8.2amended

i18next-http-middleware has path traversal / SSRF via user-controlled language and namespace parameters

CVE-2026-42353GHSA-jfgf-83c5-2c4m

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (i18next-http-middleware 3.9.3), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
8.2 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
EPSS
  • CVE-2026-42353: 0.39% estimated exploitation activity in the next 30 days; percentile 32.80 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary Versions of i18next-http-middleware prior to 3.9.3 pass the user-controlled lng and ns values from getResourcesHandler directly into i18next.services.backendConnector.load(languages, namespaces, …) without any sanitisation. Depending on which backend is configured, the unvalidated path segments enable one of two attacks: - Filesystem path traversal when the middleware is paired with i18next-fs-backend (or any backend that interpolates lng / ns into a filesystem path). - Server-Side Request Forgery (SSRF) when the middleware is paired with i18next-http-backend (or any backend that interpolates into an HTTP URL). Example request: with i18next-fs-backend reads the attacker-chosen file from disk; with i18next-http-backend reshapes the outgoing URL to target an internal service. Impact - Arbitrary file read via fs-style backends — any file the Node process can read becomes reachable (source, configuration, .ssh keys, .env, Docker secrets, etc.). - SSRF via http-style backends —…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-jfgf-83c5-2c4m

  2. Revision 1 · created ·

    Published from osv record GHSA-jfgf-83c5-2c4m

Agent brief

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# Patch Next advisory brief: CVE-2026-42353

Advisory: i18next-http-middleware has path traversal / SSRF via user-controlled language and namespace parameters
IDs: CVE-2026-42353, GHSA-jfgf-83c5-2c4m
Record: https://patchnext.com/advisories/cve-2026-42353 (revision 2, source checked 26 Oct 2026, 12:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: i18next-http-middleware 3.9.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm i18next-http-middleware: affected < 3.9.3; fixed in 3.9.3

## Suggested inspection (read-only)
- `npm ls i18next-http-middleware --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-middleware.
- 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-jfgf-83c5-2c4m (OSV record GHSA-jfgf-83c5-2c4m lists affected ranges: npm i18next-http-middleware >=0 <3.9.3 (fixed))
- Verified: https://github.com/advisories/GHSA-jfgf-83c5-2c4m (GitHub-reviewed advisory GHSA-jfgf-83c5-2c4m lists affected ranges: npm i18next-http-middleware >=0 <3.9.3)

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