Vulnerabilities

Trojan.Win32.Pincav.cmfl Insecure Permissions

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/9d296ebd6b4f79457fcc61e38dcce61e.txt
Contact: malvuln13@gmail.com
Media: twitter.co Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/9d296ebd6b4f79457fcc61e38dcce61e.txt
Contact: malvuln13@gmail.com
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_USERSoftwareMicrosoftWindowsCurrentVersionRun 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 ... ");
puts("Restart your computer ...");

puts("[+] Trojan.Win32.Pincav.cmfl PWNED! ");
puts("[+] MD5: 9d296ebd6b4f79457fcc61e38dcce61e ");
puts("[+] By Malvuln ");
system("pause");

}

C:>cacls Windupdt
C:Windupdt BUILTINAdministrators:(OI)(CI)(ID)F
NT AUTHORITYSYSTEM:(OI)(CI)(ID)F
BUILTINUsers:(OI)(CI)(ID)R
NT AUTHORITYAuthenticated Users:(ID)C
NT AUTHORITYAuthenticated 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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