{"id":"GHSA-v8w9-8mx6-g223","summary":"Hono vulnerable to Prototype Pollution possible through __proto__ key allowed in parseBody({ dot: true })","details":"## Summary\n\nWhen using `parseBody({ dot: true })` in HonoRequest, specially crafted form field names such as `__proto__.x` could create objects containing a `__proto__` property.\n\nIf the parsed result is later merged into regular JavaScript objects using unsafe merge patterns, this may lead to prototype pollution in the target object.\n\n## Details\n\nThe `parseBody({ dot: true })` feature supports dot notation to construct nested objects from form field names.\n\nIn previous versions, the `__proto__` path segment was not filtered. As a result, specially crafted keys such as `__proto__.x` could produce objects containing `__proto__` properties.\n\nWhile this behavior does not directly modify `Object.prototype` within Hono itself, it may become exploitable if the parsed result is later merged into regular JavaScript objects using unsafe merge patterns.\n\n## Impact\n\nApplications that merge parsed form data into regular objects using unsafe patterns (for example recursive deep merge utilities) may become vulnerable to prototype pollution.","aliases":["CVE-2026-56763"],"modified":"2026-09-10T03:50:41.168738778Z","published":"2026-03-11T00:31:47Z","database_specific":{"cwe_ids":["CWE-1321"],"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2026-03-11T00:31:47Z","nvd_published_at":null},"references":[{"type":"WEB","url":"https://github.com/honojs/hono/security/advisories/GHSA-v8w9-8mx6-g223"},{"type":"WEB","url":"https://github.com/honojs/hono/commit/ef902257e0beacbb83d2a9549b3b83e03514a6fe"},{"type":"PACKAGE","url":"https://github.com/honojs/hono"}],"affected":[{"package":{"name":"hono","ecosystem":"npm","purl":"pkg:npm/hono"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"4.12.7"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-v8w9-8mx6-g223/GHSA-v8w9-8mx6-g223.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N"}]}