Backdoor.Win32.Agent.xs malware suffers from an insecure permissions vulnerability.
d2916061c5f8b68a3a9d24232b67ad6eDiscovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/6c51a5ba17ffd317ad08541e20131ef3.txt
Contact: [email protected]
Media: twitter.com/malvuln
Threat: Backdoor.Win32.Agent.xs
Vulnerability: Insecure Permissions
Description: The malware creates a hidden but insecure dir named "Recycler" under c:\ drive and grants change (C) permissions to the authenticated user group. It also drops an exe named "explorer.exe", standard users can rename the malware and reboot to disable it or replace with their own executable to escalate privileges when a privileged user logs on to the infected machine.
Type: PE32
MD5: 6c51a5ba17ffd317ad08541e20131ef3
Vuln ID: MVID-2021-0106
Dropped files: explorer.exe
Disclosure: 02/23/2021
Exploit/PoC:
void main(void){
puts("[+] Unhiding the malware to rename it...");
system("attrib -h C:\\Recycler\\explorer.exe");
system("RENAME C:\\Recycler\\explorer.exe 13");
Sleep(1000);
printf("[+] Disabled by renaming C:\\Recycler\\explorer.exe to 13 ...\n");
printf("[+] Restart your computer ...\n");
Sleep(1000);
puts("[+] Backdoor.Win32.Agent.xs PWNED!");
puts("[+] MD5: 6c51a5ba17ffd317ad08541e20131ef3");
puts("[+] By Malvuln");
system("pause");
}
C:\>cacls \Recycler
C:\Recycler 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 \Recycler
Volume in drive C has no label.
Directory of C:\Recycler
02/16/2021 04:19 PM <DIR> .
02/16/2021 04:19 PM <DIR> ..
02/16/2021 04:19 PM 77,824 explorer.exe
1 File(s) 77,824 bytes
2 Dir(s) 62,863,994,880 bytes free
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