{"id":"CVE-2026-48714","revision":"e197d28441eb4200bcea12b3183d228a","records":[{"revision":"e197d28441eb4200bcea12b3183d228a","observedAt":"2026-10-27T13:11:53.172+00:00","statement":{"source":"nvd","id":"CVE-2026-48714","aliases":[],"title":"i18next-http-middleware is a middleware to be used with Node.js web frameworks like express or Fastify and also for Deno. In versions prior to 3.9.7, the missingKeyHandler blocked the literal request-body keys __proto__, constructor, and pr…","description":"i18next-http-middleware is a middleware to be used with Node.js web frameworks like express or Fastify and also for Deno. In versions prior to 3.9.7, the missingKeyHandler blocked the literal request-body keys __proto__, constructor, and prototype (added in 3.9.3, see GHSA-5fgg-jcpf-8jjw), but did not reject dotted variants such as \"__proto__.polluted\". Downstream backends that split the missing-key string on a configured keySeparator (notably i18next-fs-backend ≤ 2.6.5) hand these keys to an unguarded setPath() walker that writes to Object.prototype. Applications that expose missingKeyHandler to untrusted input AND use i18next-fs-backend ≤ 2.6.5 are directly exploitable for remote prototype pollution. Other downstream backends that split the missing-key string the same way may be similarly affected. Depending on the host application, polluted prototype properties may cause crashes, corrupted translation behaviour, configuration poisoning, or bypasses of property-based security checks. This issue has been fixed in version 3.9.7.  If developers cannot upgrade immediately, they should do the following: do not expose missingKeyHandler to untrusted users (mount it behind authentication, or remove the route), add a request-body filter ahead of the handler that rejects any top-level key containing __proto__, constructor, or prototype after splitting on their configured keySeparator, and disable missing-key persistence (saveMissing: false) when accepting writes from untrusted input.","state":0,"publishedAt":"2026-06-15T22:16:17.55+00:00","modifiedAt":"2026-10-25T23:10:00.167+00:00","affected":[],"metrics":[{"system":"CVSS 3.1 · security-advisories@github.com · Secondary","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","score":9.1,"severity":"CRITICAL"}],"references":["https://github.com/i18next/i18next-http-middleware/commit/7c6d26f137d3e940b8d229ca148bca38845faf49","https://github.com/i18next/i18next-http-middleware/security/advisories/GHSA-f49m-vf83-692w"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-48714","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Analyzed","weaknesses":["CWE-1321"],"productCriteria":["cpe:2.3:a:i18next:i18next-http-middleware:*:*:*:*:*:node.js:*:*"],"sourceDates":{"published":"2026-06-15T22:16:17.550","lastModified":"2026-10-25T23:10:00.167"},"relatedAdvisories":[],"note":"NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-48714","identifiers":["CVE-2026-48714"]},"retained":false,"historicalAffected":[]}],"coverage":[]}