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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.
This 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.
Impact
This 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.
Mitigation
This 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.
Details
Suppose 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:
const JSON5 = require('json5');
const doSomethingDangerous = (props) => {
if (props.isAdmin) {
console.log('Doing dangerous thing as admin.');
} else {
console.log('Doing dangerous thing as user.');
}
};
const secCheckKeysSet = (obj, searchKeys) => {
let searchKeyFound = false;
Object.keys(obj).forEach((key) => {
if (searchKeys.indexOf(key) > -1) {
searchKeyFound = true;
}
});
return searchKeyFound;
};
const props = JSON5.parse('{"foo": "bar"}');
if (!secCheckKeysSet(props, ['isAdmin', 'isMod'])) {
doSomethingDangerous(props); // "Doing dangerous thing as user."
} else {
throw new Error('Forbidden...');
}
If the user attempts to set the isAdmin key, their request will be rejected:
However, 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:
const props = JSON5.parse('{"foo": "bar", "__proto__": {"isAdmin": true}}');
if (!secCheckKeysSet(props, ['isAdmin', 'isMod'])) {
doSomethingDangerous(props); // "Doing dangerous thing as admin."
} else {
throw new Error('Forbidden...');
}
Configuration
š Schedule: Branch creation - "" (UTC), Automerge - At any time (no schedule defined).
š¦ Automerge: Disabled by config. Please merge this manually once you are satisfied.
ā» Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.
š Ignore: Close this PR and you won't be reminded about this update again.
[ ] If you want to rebase/retry this PR, check this box
This PR has been generated by Mend Renovate. View repository job log here.
This PR contains the following updates:
1.0.1
->1.0.2
GitHub Vulnerability Alerts
CVE-2022-46175
The
parse
method of the JSON5 library before and including version2.2.1
does not restrict parsing of keys named__proto__
, allowing specially crafted strings to pollute the prototype of the resulting object.This 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.Impact
This 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.Mitigation
This 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.
Details
Suppose 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:If the user attempts to set the
isAdmin
key, their request will be rejected:However, users can instead set the
__proto__
key to{"isAdmin": true}
.JSON5
will parse this key and will set theisAdmin
key on the prototype of the returned object, allowing the user to bypass the security check and run their request as an admin:Configuration
š Schedule: Branch creation - "" (UTC), Automerge - At any time (no schedule defined).
š¦ Automerge: Disabled by config. Please merge this manually once you are satisfied.
ā» Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.
š Ignore: Close this PR and you won't be reminded about this update again.
This PR has been generated by Mend Renovate. View repository job log here.