{"id":"CVE-2026-42353","aliases":["EUVD-2026-28797","GHSA-jfgf-83c5-2c4m"],"status":"published","title":"Path traversal / SSRF in i18next-http-middleware via user-controlled language and namespace parameters","description":"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":{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00387,"percentile":0.3302,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-22","CWE-918"],"published":"2026-04-29T22:26:36Z","modified":"2026-10-28T02:30:20Z","fixes":[{"ecosystem":"npm","package":"i18next-http-middleware","fixed_in":["3.9.3"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"npm","package":"i18next-http-middleware","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.9.3"}]}]},{"source":"osv","ecosystem":"npm","package":"i18next-http-middleware","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"3.9.3"}]}]}],"products":[{"vendor":"i18next","product":"i18next-http-middleware"}],"references":[{"url":"https://github.com/i18next/i18next-http-middleware/security/advisories/GHSA-jfgf-83c5-2c4m","tags":["x_refsource_CONFIRM","advisory","web"]},{"url":"https://www.i18next.com/how-to/faq#how-should-the-language-codes-be-formatted","tags":["web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-42353","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-jfgf-83c5-2c4m"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/42xxx/CVE-2026-42353.json","tags":["advisory"]},{"url":"https://github.com/i18next/i18next-http-middleware","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-42353","title":"Path traversal / SSRF in i18next-http-middleware via user-controlled language and namespace parameters","description":"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.","status":"published","published":"2026-05-08T15:29:55.9Z","modified":"2026-05-08T23:30:15.045Z","cvss":[{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N","level":"high","assessor":"cna"}],"cwes":["CWE-22","CWE-918"],"updated_at":"2026-11-02T13:40:23.731501Z"}],"euvd":[{"id":"EUVD-2026-28797","description":"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.","status":"published","published":"2026-05-08T15:29:55Z","modified":"2026-05-08T23:30:15Z","cvss":[{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N","level":"high"}],"updated_at":"2026-11-02T19:05:14.089367Z"}],"ghsa":[{"id":"GHSA-jfgf-83c5-2c4m","title":"i18next-http-middleware has path traversal / SSRF via user-controlled language and namespace parameters","description":"### 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, …)` 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 — any file the Node process can read becomes reachable (source, configuration, `.ssh` keys, `.env`, Docker secrets, etc.).\n- **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.\n- **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.\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 — 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)) — 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` ≥ 2.6.4, `i18next-http-backend` ≥ 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) — 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) — 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)","status":"published","published":"2026-04-29T22:26:36Z","modified":"2026-05-13T13:30:17Z","cvss":[{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N","level":"high"}],"cwes":["CWE-22","CWE-918"],"updated_at":"2026-11-02T14:40:07.01746Z"}],"nvd":[{"id":"CVE-2026-42353","description":"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.","status":"published","published":"2026-05-08T16:16:12.197Z","modified":"2026-10-26T18:10:00.173Z","cvss":[{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N","level":"high","assessor":"secondary"}],"cwes":["CWE-22","CWE-918"],"updated_at":"2026-11-02T14:12:17.842772Z"}],"osv":[{"id":"CVE-2026-42353","title":"Path traversal / SSRF in i18next-http-middleware via user-controlled language and namespace parameters","description":"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.","status":"published","published":"2026-05-08T15:29:55.9Z","modified":"2026-10-28T02:30:20.908405975Z","cvss":[{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N","level":"high"}],"cwes":["CWE-22","CWE-918"],"updated_at":"2026-11-02T15:45:04.117819Z"},{"id":"GHSA-jfgf-83c5-2c4m","title":"i18next-http-middleware has path traversal / SSRF via user-controlled language and namespace parameters","description":"### 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, …)` 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 — any file the Node process can read becomes reachable (source, configuration, `.ssh` keys, `.env`, Docker secrets, etc.).\n- **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.\n- **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.\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 — 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)) — 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` ≥ 2.6.4, `i18next-http-backend` ≥ 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) — 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) — 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)","status":"published","published":"2026-04-29T22:26:36Z","modified":"2026-05-13T13:52:33.573577Z","cvss":[{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N","level":"high"}],"cwes":["CWE-22","CWE-918"],"updated_at":"2026-11-02T15:46:50.336262Z"}]}}