CVE-2026-41691

Description

Copilot said: i18nextify is a JavaScript library that adds i18nextify is a JavaScript library that adds website internationalization via a script tag, without source code changes. Versions prior to 3.0.5 interpolate the lng and ns values directly into the configured loadPath / addPath URL template without any encoding, validation, or path sanitisation. When an application exposes the language-code selection to user-controlled input (the default — i18next-browser-languagedetector reads ?lng= query params, cookies, localStorage, and request headers), an attacker can inject characters that change the structure of the outgoing request URL. This is a single URL-injection vulnerability. The attacker-controlled value is neutralised before it is used as part of an output URL string; the attack shape covers both path traversal and broader URL-structure injection — both are closed by the one interpolateUrl sanitisation fix. This issue has been fixed in version 3.0.5. If users cannot upgrade immediately, they can work around the issue by sanitising lng / ns before they reach i18next (strip .., /, \, ?, #, %, whitespace, and control characters; cap the length).

CVSS Details

CVSS Score

6.5

Severity

MEDIUM

CVSS Vector

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

Configurations (Affected Products)

No configuration data available.

i18nextify < 3.0.5

PoC / Exploit Code

⚠ For Security Research Only

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

python

// PoC for CVE-2026-41691
// Demonstrates Path Traversal via 'lng' parameter injection

// Scenario: Default loadPath is '/locales/{{lng}}/{{ns}}.json'
// Attacker sets ?lng=../../sensitive_data

const maliciousLng = "../../etc/passwd";
const ns = "translation";

// Simulated vulnerable interpolation function
function vulnerableInterpolate(template, lng, ns) {
    // Vulnerable: Direct interpolation without sanitization
    return template.replace('{{lng}}', lng).replace('{{ns}}', ns);
}

const loadPathTemplate = '/locales/{{lng}}/{{ns}}.json';
const constructedUrl = vulnerableInterpolate(loadPathTemplate, maliciousLng, ns);

console.log("Constructed Malicious URL:", constructedUrl);
// Output: /locales/../../etc/passwd/translation.json

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-41691
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-41691
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-41691/
[4] VulDB https://vuldb.com/cve/CVE-2026-41691
[5] https://github.com/i18next/i18next-http-backend/commit/4cee84f229c637b9c182366d3156f726d407a621
[6] https://github.com/i18next/i18next-http-backend/security/advisories/GHSA-q89c-q3h5-w34g

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-41691", "sourceIdentifier": "[email protected]", "published": "2026-05-07T21:16:29.560", "lastModified": "2026-05-08T16:05:43.103", "vulnStatus": "Awaiting Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "Copilot said: i18nextify is a JavaScript library that adds\ni18nextify is a JavaScript library that adds website internationalization via a script tag, without source code changes. Versions prior to 3.0.5 interpolate the lng and ns values directly into the configured loadPath / addPath URL template without any encoding, validation, or path sanitisation. When an application exposes the language-code selection to user-controlled input (the default — i18next-browser-languagedetector reads ?lng= query params, cookies, localStorage, and request headers), an attacker can inject characters that change the structure of the outgoing request URL. This is a single URL-injection vulnerability. The attacker-controlled value is neutralised before it is used as part of an output URL string; the attack shape covers both path traversal and broader URL-structure injection — both are closed by the one interpolateUrl sanitisation fix. This issue has been fixed in version 3.0.5. If users cannot upgrade immediately, they can work around the issue by sanitising lng / ns before they reach i18next (strip .., /, \\, ?, #, %, whitespace, and control characters; cap the length)."}], "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:L/I:L/A:N", "baseScore": 6.5, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 2.5}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-22"}, {"lang": "en", "value": "CWE-74"}]}], "references": [{"url": "https://github.com/i18next/i18next-http-backend/commit/4cee84f229c637b9c182366d3156f726d407a621", "source": "[email protected]"}, {"url": "https://github.com/i18next/i18next-http-backend/security/advisories/GHSA-q89c-q3h5-w34g", "source": "[email protected]"}]}}