{"id":"GHSA-f49m-vf83-692w","revision":null,"records":[{"revision":"c91918a5f50d44668ab7e9f5f21318f1","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-48714","aliases":[],"title":"i18next-http-middleware missingKeyHandler does not reject keys whose segments contain prototype-polluting names","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":"2026-06-15T20:41:49.382+00:00","modifiedAt":"2026-06-16T14:50:29.087+00:00","affected":[{"ecosystem":"Vendor product","name":"i18next-http-middleware","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"i18next\",\n                    \"product\": \"i18next-http-middleware\",\n                    \"versions\": [\n                        {\n                            \"version\": \"< 3.9.7\",\n                            \"status\": \"affected\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","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/security/advisories/GHSA-f49m-vf83-692w","https://github.com/i18next/i18next-http-middleware/commit/7c6d26f137d3e940b8d229ca148bca38845faf49"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-48714","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-48714","identifiers":["CVE-2026-48714"]},"retained":false,"historicalAffected":[]},{"revision":"64cb523e31864adc90b932d340ce2f6d","observedAt":"2026-11-07T11:30:21.354+00:00","statement":{"source":"euvd","id":"EUVD-2026-37006","aliases":["CVE-2026-48714","GHSA-f49m-vf83-692w"],"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":null,"modifiedAt":null,"affected":[],"metrics":[{"system":"EUVD CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","score":9.1,"severity":null}],"references":["https://github.com/i18next/i18next-http-middleware/security/advisories/GHSA-f49m-vf83-692w","https://github.com/i18next/i18next-http-middleware/commit/7c6d26f137d3e940b8d229ca148bca38845faf49"],"sourceUrl":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-37006","license":"ENISA EUVD · source terms and attribution apply","enrichment":{"sourceStatus":null,"weaknesses":[],"productCriteria":[],"sourceDates":{"datePublished":"Jun 15, 2026, 8:41:49 PM","dateUpdated":"Jun 16, 2026, 2:50:29 PM"},"relatedAdvisories":[],"note":"EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON."},"key":"euvd:EUVD-2026-37006","identifiers":["EUVD-2026-37006","CVE-2026-48714","GHSA-f49m-vf83-692w"]},"retained":false,"historicalAffected":[]},{"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":[]},{"revision":"204da46e9a3243a9a2abe671c982ff98","observedAt":"2026-10-24T13:17:17.793+00:00","statement":{"source":"osv","id":"GHSA-f49m-vf83-692w","aliases":["CVE-2026-48714"],"title":"i18next-http-middleware: MissingKeyHandler does not reject keys whose segments contain prototype-polluting names","description":"### Impact\n\n`i18next-http-middleware` ≤ 3.9.6's `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`.\n\nApplications 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.\n\nDepending on the host application, polluted prototype properties may cause crashes, corrupted translation behaviour, configuration poisoning, or bypasses of property-based security checks.\n\n### Patches\n\nFixed in **i18next-http-middleware 3.9.7**. A new `utils.hasUnsafeKeySegment(key, keySeparator)` helper is now used by `missingKeyHandler`; the configured `i18next.options.keySeparator` is honoured (default `.`; `false` disables segment splitting and only the literal-key denylist applies). Legitimate dotted keys (e.g. `\"header.title\"`) are unaffected.\n\nThe root-cause fix has been shipped in `i18next-fs-backend` **2.6.6** — see the companion advisory.\n\n### Workarounds\n\nIf users cannot upgrade immediately:\n\n- Do not expose `missingKeyHandler` to untrusted users (mount it behind authentication, or remove the route).\n- Add a request-body filter ahead of the handler that rejects any top-level key containing `__proto__`, `constructor`, or `prototype` after splitting on a configured `keySeparator`.\n- Disable missing-key persistence (`saveMissing: false`) when accepting writes from untrusted input.\n\n### Resources\n\n- Original report by [@codeswhite](https://github.com/codeswhite).\n- Companion advisory in `i18next-fs-backend`: [GHSA-2933-q333-qg83](https://github.com/i18next/i18next-fs-backend/security/advisories/GHSA-2933-q333-qg83).\n- Previous `i18next-http-middleware` security release: GHSA-5fgg-jcpf-8jjw and GHSA-c3h8-g69v-pjrg (in 3.9.3).","state":0,"publishedAt":"2026-06-25T17:28:12+00:00","modifiedAt":"2026-06-25T17:56:29.524803+00:00","affected":[{"ecosystem":"npm","name":"i18next-http-middleware","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"3.9.7"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V3","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"CRITICAL"}],"references":["https://github.com/i18next/i18next-http-middleware/security/advisories/GHSA-f49m-vf83-692w","https://nvd.nist.gov/vuln/detail/CVE-2026-48714","https://github.com/i18next/i18next-http-middleware/commit/7c6d26f137d3e940b8d229ca148bca38845faf49","https://github.com/i18next/i18next-http-middleware"],"sourceUrl":"https://github.com/advisories/GHSA-f49m-vf83-692w","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-f49m-vf83-692w","identifiers":["GHSA-f49m-vf83-692w","CVE-2026-48714"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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