Discovery / credits: Malvuln - (c) 2022  
Original source:  
Threat: Backdoor.Win32.Jokerdoor  
Vulnerability: Weak Hardcoded Credentials  
Family: Jokerdoor  
Type: PE32  
MD5: a6437375fff871dff97dc91c8fd6259f  
Vuln ID: MVID-2022-0531  
Dropped files: Random name "awup.exe"  
Disclosure: 04/02/2022  
Description: The malware listens on TCP port 27374. The password "mathiasJ" is weak and hardcoded in the PE file. Failed authentication generates a "POPUP incorrect password..." message, using TELNET results in an error "PWDPerror reading password..." Using Nc64.exe utility results in a trailing line feed character "\n" after the supplied password. This causes the cmp statement check to fail even if the password is correct due to the "\n" character.  
004BDA0C | 8B 45 EC | mov eax,dword ptr ss:[ebp-14] | [ebp-14]:" mathiasJ\n"  
004BDA0F | 8B 15 0C AC 4D 00 | mov edx,dword ptr ds:[4DAC0C] | 004DAC0C:&"mathiasJ"  
004041C7 | 39 D0 | cmp eax,edx | eax" mathiasJ\n", edx"mathiasJ"  
So we will need to write a custom client ourselves. The password must also be sent with no space and prefixed with "PWD" E.g. "PWDmathiasJ". Upon successful authentication we get a message e.g. "PWDconnected time, date Legends 2.1".   
from socket import *  
import time  
def chk_res(s):  
while True:  
res += s.recv(512)  
if "\0" in res or "\n" in res or res == "":  
return res  
def doit():  
s=socket(AF_INET, SOCK_STREAM)  
s.connect((MALWARE_HOST, PORT))  
if __name__=="__main__":  
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