{"id":"CVE-2026-63402","aliases":[],"cve":{"records":[{"id":"CVE-2026-63402","source":"GitHub_M","state":"PUBLISHED","reasons":[],"replacements":[],"disputed":false,"unsupportedWhenAssigned":false,"reserved":"2026-07-16T19:20:28.987Z","published":"2026-10-30T22:39:07.286Z","modified":"2026-10-30T22:39:07.286Z"}],"publishers":[{"name":"GitHub_M","role":"CNA","organizationId":"a0819718-46f1-4df5-94e2-005712e83aaa","modified":"2026-10-30T22:39:07.286Z"}],"references":[{"url":"https://github.com/i18next/i18next/security/advisories/GHSA-6jcc-5g8w-32mx","tags":["x_refsource_CONFIRM"],"source":"GitHub_M"},{"url":"https://github.com/i18next/i18next/commit/642137b7786d83661ec3ee53027798dc4b81d30a","tags":["x_refsource_MISC"],"source":"GitHub_M"},{"url":"https://github.com/i18next/i18next/tree/v26.3.4","tags":["x_refsource_MISC"],"source":"GitHub_M"}],"weaknesses":[{"id":"CWE-471","description":"CWE-471: Modification of Assumed-Immutable Data (MAID)","source":"GitHub_M"},{"id":"CWE-1321","description":"CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')","source":"GitHub_M"}],"applicability":[],"prioritization":[]},"title":"i18next: Shared built-in corruption through inherited-key deepExtend recursion","titleSource":"GitHub_M","descriptionSource":"GitHub_M","description":"i18next is an internationalization framework for JavaScript. Prior to version 26.3.4, `deepExtend` in `src/utils.js` checks property existence with the in operator and recurses into inherited built-ins reached through `Object.prototype`. An application must explicitly pass attacker-controlled resource data to `addResourceBundle(lng, ns, data, deep, overwrite)` with both `deep: true` and `overwrite: true`. Source keys such as `hasOwnProperty`, `toString` and `valueOf` can then select shared inherited built-in function objects, and a nested value can overwrite a property of those objects process-wide. For example, making `Object.prototype.hasOwnProperty.call` non-callable causes subsequent uses, including i18next internals, to throw TypeError, resulting in unrecoverable denial of service and limited integrity impact. The `__proto__`/`constructor` guard does not prevent this mechanism because the corruption target is an inherited built-in function rather than the prototype object itself. Default calls without deep merging or with overwrite falsy are unaffected, and no standard i18next backend or integration uses the vulnerable configuration. This issue is distinct from the setPath/key-walking prototype-pollution flaws in i18next-fs-backend (CVE-2026-48713) and i18next-http-middleware (CVE-2026-48714). This issue is fixed in version 26.3.4.","score":5.9,"severity":"medium","published":"2026-10-30T22:39:07.286Z","modified":"2026-10-30T22:39:07.286Z","withdrawn":false,"knownExploited":false,"affected":[],"products":[{"vendor":"i18next","name":"i18next","platforms":[],"versions":[{"version":"< 26.3.4","status":"affected"}],"cpes":[],"source":"GitHub_M","url":"https://www.cve.org/CVERecord?id=CVE-2026-63402"}],"remediation":[],"references":["https://github.com/i18next/i18next/security/advisories/GHSA-6jcc-5g8w-32mx","https://github.com/i18next/i18next/commit/642137b7786d83661ec3ee53027798dc4b81d30a","https://github.com/i18next/i18next/tree/v26.3.4"],"sources":[{"name":"CVE","id":"CVE-2026-63402","modified":"2026-10-30T22:39:07.286Z","url":"https://www.cve.org/CVERecord?id=CVE-2026-63402"}],"assessments":[{"source":"GitHub_M","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:H","score":5.9}],"sourceAffected":[],"observedAt":"2026-10-31T00:00:24.584Z","kev":{"status":"not-listed","checkedAt":"2026-10-31T03:05:31.332Z"},"coverage":[{"source":"NVD","status":"available","checkedAt":"2026-10-31T00:05:36.616Z","attemptedAt":"2026-10-31T00:05:36.616Z"},{"source":"GHSA","status":"no-result","checkedAt":"2026-10-31T00:05:36.574Z","attemptedAt":"2026-10-31T00:05:36.574Z"},{"source":"EUVD","status":"available","checkedAt":"2026-10-31T00:05:37.575Z","attemptedAt":"2026-10-31T00:05:37.575Z"},{"source":"EPSS","status":"no-result","checkedAt":"2026-10-31T00:05:36.091Z","attemptedAt":"2026-10-31T00:05:36.091Z"}],"evidence":[{"source":"NVD","id":"CVE-2026-63402","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63402","modified":"2026-10-30T23:17:15.400","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:H","checkedAt":"2026-10-31T00:05:36.616Z"},{"source":"ENISA EUVD","id":"EUVD-2026-114546","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-114546","modified":"Oct 30, 2026, 10:39:07 PM","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:H","checkedAt":"2026-10-31T00:05:37.575Z"}],"aiSummary":{"text":"i18next versions prior to 26.3.4 have a vulnerability where an attacker can corrupt shared built-in objects if they can pass controlled data to `addResourceBundle` with `deep` and `overwrite` set to true. This can lead to a denial of service. The issue is fixed in version 26.3.4.","model":"@cf/meta/llama-3.3-70b-instruct-fp8-fast","generatedAt":"2026-10-31T00:11:04.623Z","sources":[{"name":"CVE","url":"https://www.cve.org/CVERecord?id=CVE-2026-63402"}]}}