Trojan.Win32.Pincav.cmfl Insecure Permissions

`Discovery / credits: Malvuln - malvuln.com (c) 2021  
Original source: https://malvuln.com/advisory/9d296ebd6b4f79457fcc61e38dcce61e.txt  
Contact: [email protected]  
Media: twitter.com/malvuln  
  
Threat: Trojan.Win32.Pincav.cmfl  
Vulnerability: Insecure Permissions   
Description: The trojan creates an insecure dir named "Windupdt" under c:\ drive, granting change (C) permissions to authenticated users group. Standard users can rename the malware and reboot to disable it or replace it with their own executable to escalate privileges when a privileged user logs on. The malware also creates registry key under HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run for persistence. To successfully rename the malware we have to call Windows "attrib -h" command to unhide the executable or the rename will fail.  
Type: PE32  
MD5: 9d296ebd6b4f79457fcc61e38dcce61e  
Vuln ID: MVID-2021-0104  
Dropped files: winupdate.exe  
Disclosure: 02/21/2021  
  
Exploit/PoC:  
#include "stdio.h"  
#include "windows.h"  
  
void main(void){  
  
system("attrib -h C:\\Windupdt\\winupdate.exe");  
puts("Unhiding the malware to rename it...");  
system("RENAME C:\\Windupdt\\winupdate.exe 13");  
  
Sleep(1000);  
puts("[+] Disabled persistence by renaming winupdate.exe to 13 ...\n");  
puts("Restart your computer ...");  
  
puts("[+] Trojan.Win32.Pincav.cmfl PWNED!\n");  
puts("[+] MD5: 9d296ebd6b4f79457fcc61e38dcce61e\n");  
puts("[+] By Malvuln\n");  
system("pause");  
  
}  
  
C:\>cacls Windupdt  
C:\Windupdt 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  
  
  
C:\>dir /a \Windupdt  
Volume in drive C has no label.  
  
Directory of C:\Windupdt  
  
06/14/2012 11:46 PM 707,094 winupdate.exe  
1 File(s) 707,094 bytes  
2 Dir(s) 49,773,490,176 bytes free  
  
  
  
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`