Document Title:
===============
MP3 Cutter 1.1.0 - Reverse Engineering Issue


Release Date:
=============
2016-09-05


Vulnerability Disclosure Timeline:
==================================
2016-09-15:  Public Disclosure


Common Vulnerability Scoring System:
====================================
6


Product & Service Introduction:
===============================
MP3 Cutter is a Windows desktop utility allows you to cut and split a big MP3 or video to small audio pieces. 
With MP3 Cutter, you can split and cut not only MP3 format, but also WMA, WAV, AMR, WMV, AVI, MPG, 3GP, MP4, FLAC, 
OGG, WMV, MOV and more than 40 audio & video formats. 

(Copy of the Vendor Homepage: http://www.mp3cutter.org/)


Affected Product(s):
====================
Product: MP3 Cutter v1.1.0


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


Severity Level:
===============
High


Technical Details & Description:
================================
A Reverse Enginering Vulnerability has been discovered in the official MP3 Cutter v1.1.0 software.

An attacker could make the software completely free MP3 Cutter manipulating conditoinel jumps and bypass security registration code to back any password and validated registration.

Vulnerable Input(s):
      [+] Registration Code


Proof of Concept (PoC):
=======================
A Reverse Enginering Vulnerability can be exploited by local attackers with low privileged system user account.
For security demonstration or to reproduce the vulnerability follow the provided information and steps below to continue.

Manual steps to reproduce the vulnerability ...
1. Debug MP3 Cutter.exe
2. Find the string "Invaild Serial Code"
3. Replace the conditional jump "JMP" in "JNZ"
4. Save the changes made and save the executable
5. Run the software you have changed
6. Click "Register MP3 Cutter now"
7. Enter any code in "Input Registration Code" eg 12345 and click "OK"
8. BOOMM Registration Hijacked.


Security Risk:
==============
The security risk of the reverse engineering vulnerability in the software core is estimated as high. (CVSS 6.0)

--- PoC : Exploit ---
0067C193   E9 5A010000      JMP MP3Cutte.0067C2F2             <-- Handle the conditional jump JMP to (JNZ MP3Cutte.0067C2F2)
0067C198   C745 FC 13000000 MOV DWORD PTR SS:[EBP-4],13
0067C19F   C785 60FFFFFF 04>MOV DWORD PTR SS:[EBP-A0],80020004
0067C1A9   C785 58FFFFFF 0A>MOV DWORD PTR SS:[EBP-A8],0A
0067C1B3   C785 70FFFFFF 04>MOV DWORD PTR SS:[EBP-90],80020004
0067C1BD   C785 68FFFFFF 0A>MOV DWORD PTR SS:[EBP-98],0A
0067C1C7   C785 40FFFFFF 38>MOV DWORD PTR SS:[EBP-C0],MP3Cutte.005BE>; UNICODE "Invaild"
0067C1D1   C785 38FFFFFF 08>MOV DWORD PTR SS:[EBP-C8],8
0067C1DB   8D95 38FFFFFF    LEA EDX,DWORD PTR SS:[EBP-C8]
0067C1E1   8D8D 78FFFFFF    LEA ECX,DWORD PTR SS:[EBP-88]
0067C1E7   E8 3271D8FF      CALL <JMP.&MSVBVM60.__vbaVarDup>
0067C1EC   C785 50FFFFFF 08>MOV DWORD PTR SS:[EBP-B0],MP3Cutte.005BE>; UNICODE "Invaild Serial Code."


[+] Disclaimer [+]
===================
Permission is hereby granted for the redistribution of this advisory, provided that it is not altered except by reformatting it, and that due credit is given. Permission is explicitly given for insertion in vulnerability databases and similar, provided that due credit is given to the author.
The author is not responsible for any misuse of the information contained herein and prohibits any malicious use of all security related information or exploits by the author or elsewhere.


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Advisory:   www.vulnerability-lab.com/show.php?user=ZwX


                             Copyright A(c) 2016 | ZwX - Security Researcher (Software & web application)