{"id":"CVE-2026-56763","aliases":["EUVD-2026-43173","GHSA-3wcj-gjvf-fvch","GHSA-v8w9-8mx6-g223"],"status":"published","title":"Hono - Prototype Pollution via __proto__ Key in parseBody with dot Option","description":"Hono before 4.12.7 allows __proto__ key in parseBody with dot option enabled, permitting specially crafted form field names to create objects with __proto__ properties. When parsed results are merged into regular JavaScript objects using unsafe merge patterns, attackers can exploit this to achieve prototype pollution and modify object behavior.","severity":{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00273,"percentile":0.19891,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-1321"],"published":"2026-03-11T00:31:47Z","modified":"2026-10-28T02:30:29Z","fixes":[{"ecosystem":"npm","package":"hono","fixed_in":["4.12.7"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"npm","package":"hono","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.12.7"}]}]},{"source":"osv","ecosystem":"npm","package":"hono","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"4.12.7"}]}]}],"products":[{"vendor":"hono","product":"hono"},{"vendor":"honojs","product":"hono"}],"references":[{"url":"https://github.com/honojs/hono/security/advisories/GHSA-v8w9-8mx6-g223","tags":["vendor-advisory","advisory","web"]},{"url":"https://www.vulncheck.com/advisories/hono-prototype-pollution-via-proto-key-in-parsebody-with-dot-option","tags":["third-party-advisory","advisory","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-56763","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-3wcj-gjvf-fvch"},{"url":"https://github.com/honojs/hono/commit/ef902257e0beacbb83d2a9549b3b83e03514a6fe","tags":["web"]},{"url":"https://github.com/advisories/GHSA-v8w9-8mx6-g223"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/56xxx/CVE-2026-56763.json","tags":["advisory"]},{"url":"https://github.com/honojs/hono","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-56763","title":"Hono - Prototype Pollution via __proto__ Key in parseBody with dot Option","description":"Hono before 4.12.7 allows __proto__ key in parseBody with dot option enabled, permitting specially crafted form field names to create objects with __proto__ properties. When parsed results are merged into regular JavaScript objects using unsafe merge patterns, attackers can exploit this to achieve prototype pollution and modify object behavior.","status":"published","published":"2026-07-11T13:00:59.084Z","modified":"2026-07-14T14:30:12.573Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium","assessor":"cna"},{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-1321"],"updated_at":"2026-11-02T13:37:02.780526Z"}],"euvd":[{"id":"EUVD-2026-43173","description":"Hono before 4.12.7 allows __proto__ key in parseBody with dot option enabled, permitting specially crafted form field names to create objects with __proto__ properties. When parsed results are merged into regular JavaScript objects using unsafe merge patterns, attackers can exploit this to achieve prototype pollution and modify object behavior.","status":"published","published":"2026-07-11T13:00:59Z","modified":"2026-07-14T14:30:12Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"updated_at":"2026-11-02T18:19:59.713046Z"}],"ghsa":[{"id":"GHSA-3wcj-gjvf-fvch","title":"Duplicate Advisory: Hono vulnerable to Prototype Pollution possible through __proto__ key allowed in parseBody({ dot: true })","description":"## Duplicate Advisory\n\nThis advisory has been withdrawn because it is a duplicate of GHSA-v8w9-8mx6-g223. This link is maintained to preserve external references.\n\n## Original Description\n\nHono before 4.12.7 allows __proto__ key in parseBody with dot option enabled, permitting specially crafted form field names to create objects with __proto__ properties. When parsed results are merged into regular JavaScript objects using unsafe merge patterns, attackers can exploit this to achieve prototype pollution and modify object behavior.","status":"withdrawn","published":"2026-07-11T15:30:23Z","modified":"2026-10-02T22:36:00Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium"},{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-1321"],"updated_at":"2026-11-02T14:41:24.739884Z"},{"id":"GHSA-v8w9-8mx6-g223","title":"Hono vulnerable to Prototype Pollution possible through __proto__ key allowed in parseBody({ dot: true })","description":"## 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.","status":"published","published":"2026-03-11T00:31:47Z","modified":"2026-10-02T22:36:06Z","cvss":[{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-1321"],"updated_at":"2026-11-02T14:41:24.739884Z"}],"nvd":[{"id":"CVE-2026-56763","description":"Hono before 4.12.7 allows __proto__ key in parseBody with dot option enabled, permitting specially crafted form field names to create objects with __proto__ properties. When parsed results are merged into regular JavaScript objects using unsafe merge patterns, attackers can exploit this to achieve prototype pollution and modify object behavior.","status":"published","published":"2026-07-11T14:16:22.08Z","modified":"2026-10-25T15:10:00.147Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium","assessor":"secondary"},{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium","assessor":"secondary"}],"cwes":["CWE-1321"],"updated_at":"2026-11-02T14:12:28.771746Z"}],"osv":[{"id":"CVE-2026-56763","title":"Hono - Prototype Pollution via __proto__ Key in parseBody with dot Option","description":"Hono before 4.12.7 allows __proto__ key in parseBody with dot option enabled, permitting specially crafted form field names to create objects with __proto__ properties. When parsed results are merged into regular JavaScript objects using unsafe merge patterns, attackers can exploit this to achieve prototype pollution and modify object behavior.","status":"published","published":"2026-07-11T13:00:59.084Z","modified":"2026-10-28T02:30:29.679468508Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"cwes":["CWE-1321"],"updated_at":"2026-11-02T15:45:11.609219Z"},{"id":"GHSA-3wcj-gjvf-fvch","title":"Duplicate Advisory: Hono vulnerable to Prototype Pollution possible through __proto__ key allowed in parseBody({ dot: true })","description":"## Duplicate Advisory\n\nThis advisory has been withdrawn because it is a duplicate of GHSA-v8w9-8mx6-g223. This link is maintained to preserve external references.\n\n## Original Description\n\nHono before 4.12.7 allows __proto__ key in parseBody with dot option enabled, permitting specially crafted form field names to create objects with __proto__ properties. When parsed results are merged into regular JavaScript objects using unsafe merge patterns, attackers can exploit this to achieve prototype pollution and modify object behavior.","status":"withdrawn","published":"2026-07-11T15:30:23Z","modified":"2026-10-02T22:45:04.331285767Z","cvss":[{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium"},{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium"}],"cwes":["CWE-1321"],"updated_at":"2026-11-02T15:46:36.092962Z"},{"id":"GHSA-v8w9-8mx6-g223","title":"Hono vulnerable to Prototype Pollution possible through __proto__ key allowed in parseBody({ dot: true })","description":"## 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.","status":"published","published":"2026-03-11T00:31:47Z","modified":"2026-10-02T22:45:04.525587715Z","cvss":[{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-1321"],"updated_at":"2026-11-02T15:46:56.981655Z"}]}}