Document Title: =============== MP3 Cutter 1.1.0 - Reverse Engineering Issue Date: ===== 2016-10-05 References: =========== https://www.vulnerability-lab.com/get_content.php?id=1937 VL-ID: ===== 1937 Common Vulnerability Scoring System: ==================================== 6 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 Homepage: http://www.mp3cutter.org/) Abstract: ========= An independent vulnerability laboratory researcher discovered a reverse engineering issue in the official MP3 Cutter v1.1.0 software. Report-Timeline: ================ 2016-09-05: Public Disclosure (Vulnerability Laboratory) Status: ======== Published Affected Products: ================== Exploitation-Technique: ======================= Local Severity: ========= High Details: ======== A reverse enginering issue has been discovered in the official MP3 Cutter v1.1.0 software. An attacker could make the software completely free MP3 Cutter manipulating conditional jumps to bypass the security registration code to back any password and validated registration. Vulnerable Input(s): [+] Registration Code Proof of Concept: ================= The reverse enginering issue 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 issue ... 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. Registration Hijacked successful! --- Debug Exploitation Logs --- 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 0067C1EC C785 50FFFFFF 08>MOV DWORD PTR SS:[EBP-B0],MP3Cutte.005BE>; UNICODE "Invaild Serial Code." Risk: ===== The security risk of the reverse engineering issue in the software core is estimated as high. (CVSS 6.0) Credits: ======== ZwX - [http://www.vulnerability-lab.com/show.php?user=ZwX] Disclaimer: =========== The information provided in this advisory is provided as it is without any warranty. Vulnerability Lab disclaims all warranties, either expressed or implied, including the warranties of merchantability and capability for a particular purpose. Vulnerability-Lab or its suppliers are not liable in any case of damage, including direct, indirect, incidental, consequential loss of business profits or special damages, even if Vulnerability-Lab or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability mainly for consequential or incidental damages so the foregoing limitation may not apply. We do not approve or encourage anybody to break any licenses, policies, deface websites, hack into databases or trade with stolen data. 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