Document Title: =============== FLV To MP3 Converter 3.0.5 - Reverse Engineering Issue Date: ===== 2016-09-13 References: =========== https://www.vulnerability-lab.com/get_content.php?id=1938 VL-ID: ===== 1938 Common Vulnerability Scoring System: ==================================== 6 Introduction: ============= Most converters can convert MP4 video to MP3 only, but don't support YouTube FLV files. FLV To MP3 Converter is a windows program that fast converts FLV To MP3 audio format. FLV To MP3 Converter also supports MP4, MPG, WMV, MOV and more video formats to MP3 and other audio formats conversion. (Copy of the Homepage: http://www.flvmp3.net/) Abstract: ========= An independent vulnerability laboratory researcher discovered a reverse engineering vulnerability in the official FLV To MP3 Converter 3.0.5 software. Report-Timeline: ================ 2016-09-05: Public Disclosure (Vulnerability Laboratory) Status: ======== Published Affected Products: ================== Exploitation-Technique: ======================= Local Severity: ========= High Details: ======== A reverse enginering vulnerability has been discovered in the official FLV To MP3 Converter 3.0.5 software. An attacker could make the software completely free FLV To MP3 Converter manipulating conditoinel jumps and bypass security registration code to back any password and validated registration. Vulnerable Input(s): [+] Registration Code Proof of Concept: ================= The 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 FLV To MP3 Converter.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 FLV To MP3 Converter now" 7. Enter any code in "Input Registration Code" eg VulnerabilityLabs and click "OK" 8. BOOMM Registration Hijacked. --- PoC: Exploit Code --- 005F24F9 . E9 B0000000 JMP FLVToMP3.005F25AE <-- Handle the conditional jump JMP to (JNZ FLVToMP3.005F25AE) 005F24FE > C745 FC 130000>MOV DWORD PTR SS:[EBP-4],13 005F2505 . C785 78FFFFFF >MOV DWORD PTR SS:[EBP-88],80020004 005F250F . C785 70FFFFFF >MOV DWORD PTR SS:[EBP-90],0A 005F2519 . C745 88 040002>MOV DWORD PTR SS:[EBP-78],80020004 005F2520 . C745 80 0A0000>MOV DWORD PTR SS:[EBP-80],0A 005F2527 . C785 58FFFFFF >MOV DWORD PTR SS:[EBP-A8],FLVToMP3.00554>; UNICODE "Invaild" 005F2531 . C785 50FFFFFF >MOV DWORD PTR SS:[EBP-B0],8 005F253B . 8D95 50FFFFFF LEA EDX,DWORD PTR SS:[EBP-B0] 005F2541 . 8D4D 90 LEA ECX,DWORD PTR SS:[EBP-70] 005F2544 . E8 3F0FE1FF CALL 005F2549 . C785 68FFFFFF > MOV DWORD PTR SS:[EBP-98],FLVToMP3.00554>; UNICODE "Invaild Serial Code." Risk: ===== The security risk of the reverse engineering vulnerability 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. 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