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Trojan.Win32.Pluder.o / Insecure Permissions

CVE Category Price Severity
CWE-XXX $5000 High
Author Risk Exploitation Type Date
Unknown High Remote 2021-02-21
CVSS EPSS EPSSP
CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N 0.02192 0.50148

CVSS vector description

Our sensors found this exploit at: https://cxsecurity.com/ascii/WLB-2021020126

Below is a copy:

Trojan.Win32.Pluder.o / Insecure Permissions
Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/ee22eea131c0e00162e4ba370f396a00.txt
Contact: [email protected]
Media: twitter.com/malvuln

Threat: Trojan.Win32.Pluder.o
Vulnerability: Insecure Permissions 
Description: Creates an insecure dir named "z_Drivers" under c:\ drive, granting change (C) permissions to authenticated user group. Pluder.o also creates several registry key entries under HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run for persistence. 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. When renaming the malware it checks the dir and creates a new "svchost.exe" each time so we need to take additional step to create our own fake one in order to disable it. 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: ee22eea131c0e00162e4ba370f396a00
Vuln ID: MVID-2021-0103
Dropped files: svchost.exe
Disclosure: 02/21/2021

Exploit/PoC:
#include "stdio.h"
#include "windows.h"

void main(void){

    system("attrib -h C:\\z_Drivers\\svchost.exe");
    puts("Unhiding the malware to rename it...");
    system("RENAME C:\\z_Drivers\\svchost.exe  13");
    system("DEL /F C:\\z_Drivers\\svchost.exe");
    system("echo > C:\\z_Drivers\\svchost.exe");
  
    Sleep(1000);
    puts("[+] Disabled persistence by renaming the malware to 13 ...\n");
    puts("Created fake svchost.exe to prevent recreation");
    puts("Restart your computer ...");

    puts("[+] Trojan.Win32.Pluder.o PWNED!\n");
    puts("[+] MD5: ee22eea131c0e00162e4ba370f396a00\n");
    puts("[+] By Malvuln\n");
    system("pause");
  
}

C:\>cacls \z_Drivers
C:\z_Drivers 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 \z_Drivers
 Volume in drive C has no label.
 Directory of C:\z_Drivers
        ..
12/30/2019  03:58 AM           255,488 svchost.exe
               1 File(s)        255,488 bytes
               2 Dir(s)  49,774,018,560 bytes free





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