Sunday, May 2, 2021

HEUR.Trojan.Win32.Bayrob.gen Insecure Permissions

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/765698ccfb033c86eea6d293235d7ed0.txt
Contact: [email protected]
Media: twitter.com/malvuln

Threat: HEUR.Trojan.Win32.Bayrob.gen
Vulnerability: Insecure Permissions
Description: The malware creates a insecure dir named "rlpzeasjvgnb" under c:\ drive and grants change (C) permissions to the authenticated user group. Standard users can rename the executables dropped by the malware to disable it or replace it with their own executable. Then wait for a privileged user to logon to the infected machine to potentially escalate privileges.
Type: PE32
MD5: 765698ccfb033c86eea6d293235d7ed0
Vuln ID: MVID-2021-0191
Dropped files: mv4aefb186aghbtwsvxglk3h.exe, btqq2r, gzjegrkpac, qaazfq
Disclosure: 04/29/2021

Exploit/PoC:
C:\>cacls rlpzeasjvgnb
C:\rlpzeasjvgnb 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 rlpzeasjvgnb
Volume in drive C has no label.

Directory of C:\rlpzeasjvgnb

04/25/2021 12:21 AM 4 btqq2r
04/25/2021 12:20 AM 0 gzjegrkpac
04/25/2021 12:20 AM 222,208 mv4aefb186aghbtwsvxglk3h.exe
04/25/2021 12:20 AM 6 qaazfq
4 File(s) 222,218 bytes


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