Vulnerability-Lookup

CVE-2026-42353 (GCVE-0-2026-42353)

Vulnerability from cvelistv5 – Published: 2026-05-08 15:29 – Updated: 2026-05-08 23:30

Title

Path traversal / SSRF in i18next-http-middleware via user-controlled language and namespace parameters

Summary

i18next-http-middleware is a middleware to be used with Node.js web frameworks like express or Fastify and also for Deno. Prior to version 3.9.3, i18next-http-middleware passes the user-controlled lng and ns values from getResourcesHandler directly into i18next.services.backendConnector.load(languages, namespaces, …) without any sanitization. Depending on which backend is configured, the unvalidated path segments enable either path traversal or SSRF. This issue has been patched in version 3.9.3.

Severity ?

8.2 (High)


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

CWE

CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
CWE-918 - Server-Side Request Forgery (SSRF)

Assigner

GitHub_M

References

URL

Tags

https://github.com/i18next/i18next-http-middlewar…

x_refsource_CONFIRM

Impacted products

	Vendor	Product	Version
	i18next	i18next-http-middleware	Affected: < 3.9.3

Show details on NVD website

JSON

To clipboard

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GHSA-JFGF-83C5-2C4M

Vulnerability from github – Published: 2026-04-29 22:26 – Updated: 2026-04-29 22:26

Summary

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

Details

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:

GET /locales/resources.json?lng=../../etc/passwd&ns=root

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 — requests to internal IPs / hostnames not normally reachable from the internet; combined with cloud metadata endpoints this can escalate to credential theft.
Unbounded growth of i18next.options.ns — a now-incidental amplification: the pre-patch getResourcesHandler pushed every unique ns value into the shared i18next.options.ns singleton array without validation or bounds, enabling memory exhaustion from repeated unique payloads.

The severity is bounded by the backend in place, but the middleware itself exposed the unsanitised path; this is the "weakest link" layer.

Affected versions

< 3.9.3.

Patch

Fixed in 3.9.3. The patch introduces utils.isSafeIdentifier and applies it in getResourcesHandler before lng and ns reach the backend connector:

languages  = languages.filter(utils.isSafeIdentifier)
namespaces = namespaces.filter(utils.isSafeIdentifier)

isSafeIdentifier uses a denylist approach — it still accepts any legitimate i18next language-code shape (i18next FAQ) — rejecting:

.. sequences (relative path traversal)
path separators (/, \)
control characters (C0/C1)
prototype keys (__proto__ / constructor / prototype)
empty strings and values longer than 128 characters

Unsafe values are dropped; only safe values reach the backend. The fix is a defence-in-depth layer on top of any sanitisation the backend itself may apply.

Workarounds

No workaround short of upgrading. Front-proxying the middleware with a WAF rule that rejects requests containing .., /, \, or URL-structure characters in lng / ns is a partial mitigation. Upgrading the configured backend (i18next-fs-backend ≥ 2.6.4, i18next-http-backend ≥ 3.0.5) also closes the same attack at the next layer.

Related advisories fixed in the same release

GHSA-5fgg-jcpf-8jjw — prototype pollution via setPath and missingKeyHandler. Independently fixable, filed separately per CNA rules.
GHSA-c3h8-g69v-pjrg — HTTP response splitting + XSS-filter bypass (CVE-2026-41683).

Credits

Discovered via an internal security audit of the i18next ecosystem.

Resources

CWE-22: Path Traversal
CWE-918: Server-Side Request Forgery (SSRF) (specific sub-case when paired with an HTTP backend)
i18next FAQ: language code formatting

Severity ?

8.2 (High)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "i18next-http-middleware"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.9.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-42353"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-22",
      "CWE-918"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-29T22:26:36Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Summary\n\nVersions 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, \u2026)` without any sanitisation. Depending on which backend is configured, the unvalidated path segments enable one of two attacks:\n\n- **Filesystem path traversal** when the middleware is paired with `i18next-fs-backend` (or any backend that interpolates `lng` / `ns` into a filesystem path).\n- **Server-Side Request Forgery (SSRF)** when the middleware is paired with `i18next-http-backend` (or any backend that interpolates into an HTTP URL).\n\nExample request:\n\n```\nGET /locales/resources.json?lng=../../etc/passwd\u0026ns=root\n```\n\nwith `i18next-fs-backend` reads the attacker-chosen file from disk; with `i18next-http-backend` reshapes the outgoing URL to target an internal service.\n\n### Impact\n\n- **Arbitrary file read** via `fs`-style backends \u2014 any file the Node process can read becomes reachable (source, configuration, `.ssh` keys, `.env`, Docker secrets, etc.).\n- **SSRF** via `http`-style backends \u2014 requests to internal IPs / hostnames not normally reachable from the internet; combined with cloud metadata endpoints this can escalate to credential theft.\n- **Unbounded growth of `i18next.options.ns`** \u2014 a now-incidental amplification: the pre-patch `getResourcesHandler` pushed every unique `ns` value into the shared `i18next.options.ns` singleton array without validation or bounds, enabling memory exhaustion from repeated unique payloads.\n\nThe severity is bounded by the backend in place, but the middleware itself exposed the unsanitised path; this is the \"weakest link\" layer.\n\n### Affected versions\n\n`\u003c 3.9.3`.\n\n### Patch\n\nFixed in **3.9.3**. The patch introduces `utils.isSafeIdentifier` and applies it in `getResourcesHandler` before `lng` and `ns` reach the backend connector:\n\n```js\nlanguages  = languages.filter(utils.isSafeIdentifier)\nnamespaces = namespaces.filter(utils.isSafeIdentifier)\n```\n\n`isSafeIdentifier` uses a denylist approach \u2014 it still accepts any legitimate i18next language-code shape ([i18next FAQ](https://www.i18next.com/how-to/faq#how-should-the-language-codes-be-formatted)) \u2014 rejecting:\n\n- `..` sequences (relative path traversal)\n- path separators (`/`, `\\`)\n- control characters (C0/C1)\n- prototype keys (`__proto__` / `constructor` / `prototype`)\n- empty strings and values longer than 128 characters\n\nUnsafe values are dropped; only safe values reach the backend. The fix is a defence-in-depth layer on top of any sanitisation the backend itself may apply.\n\n### Workarounds\n\nNo workaround short of upgrading. Front-proxying the middleware with a WAF rule that rejects requests containing `..`, `/`, `\\`, or URL-structure characters in `lng` / `ns` is a partial mitigation. Upgrading the configured backend (`i18next-fs-backend` \u2265 2.6.4, `i18next-http-backend` \u2265 3.0.5) also closes the same attack at the next layer.\n\n### Related advisories fixed in the same release\n\n- [GHSA-5fgg-jcpf-8jjw](https://github.com/i18next/i18next-http-middleware/security/advisories/GHSA-5fgg-jcpf-8jjw) \u2014 prototype pollution via `setPath` and `missingKeyHandler`. Independently fixable, filed separately per CNA rules.\n- [GHSA-c3h8-g69v-pjrg](https://github.com/i18next/i18next-http-middleware/security/advisories/GHSA-c3h8-g69v-pjrg) \u2014 HTTP response splitting + XSS-filter bypass (CVE-2026-41683).\n\n### Credits\n\nDiscovered via an internal security audit of the i18next ecosystem.\n\n### Resources\n\n- [CWE-22: Path Traversal](https://cwe.mitre.org/data/definitions/22.html)\n- [CWE-918: Server-Side Request Forgery (SSRF)](https://cwe.mitre.org/data/definitions/918.html) (specific sub-case when paired with an HTTP backend)\n- [i18next FAQ: language code formatting](https://www.i18next.com/how-to/faq#how-should-the-language-codes-be-formatted)",
  "id": "GHSA-jfgf-83c5-2c4m",
  "modified": "2026-04-29T22:26:36Z",
  "published": "2026-04-29T22:26:36Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/i18next/i18next-http-middleware/security/advisories/GHSA-jfgf-83c5-2c4m"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/i18next/i18next-http-middleware"
    },
    {
      "type": "WEB",
      "url": "https://www.i18next.com/how-to/faq#how-should-the-language-codes-be-formatted"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "i18next-http-middleware has path traversal / SSRF via user-controlled language and namespace parameters"
}

FKIE_CVE-2026-42353

Vulnerability from fkie_nvd - Published: 2026-05-08 16:16 - Updated: 2026-05-08 16:16

Severity ?

8.2 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/i18next/i18next-http-middleware/security/advisories/GHSA-jfgf-83c5-2c4m

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "i18next-http-middleware is a middleware to be used with Node.js web frameworks like express or Fastify and also for Deno. Prior to version 3.9.3, i18next-http-middleware passes the user-controlled lng and ns values from getResourcesHandler directly into i18next.services.backendConnector.load(languages, namespaces, \u2026) without any sanitization. Depending on which backend is configured, the unvalidated path segments enable either path traversal or SSRF. This issue has been patched in version 3.9.3."
    }
  ],
  "id": "CVE-2026-42353",
  "lastModified": "2026-05-08T16:16:12.197",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 8.2,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 4.2,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-05-08T16:16:12.197",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/i18next/i18next-http-middleware/security/advisories/GHSA-jfgf-83c5-2c4m"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-22"
        },
        {
          "lang": "en",
          "value": "CWE-918"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2026-42353 (GCVE-0-2026-42353)

GHSA-JFGF-83C5-2C4M

Summary

Impact

Affected versions

Patch

Workarounds

Related advisories fixed in the same release

Credits

Resources

FKIE_CVE-2026-42353

Tags

Sightings

Nomenclature