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List:       full-disclosure
Subject:    [FD] Trojan.Win32.Cosmu.abix / Insecure Permissions
From:       malvuln <malvuln13 () gmail ! com>
Date:       2022-02-22 1:54:44
Message-ID: CAAHK0WS3HoeTg05sQz91upY6piKfHESkw6vgq7LYxk9FvRx7Gw () mail ! gmail ! com
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Discovery / credits: Malvuln - malvuln.com (c) 2022
Original source:
https://malvuln.com/advisory/b4638a10f7cfdbf39b9fef7539c63852.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Trojan.Win32.Cosmu.abix
Vulnerability: Insecure Permissions
Description: The malware writes several PE files and a dir with insecure
permissions under c drive granting change (C) permissions to the
authenticated user group. Standard users can rename the executable 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: b4638a10f7cfdbf39b9fef7539c63852
Vuln ID: MVID-2022-0494
Disclosure: 02/21/2022

Exploit/PoC:
C:\dump>attrib -s -h \RECYCLEP

C:\dump>dir \RECYCLEP
 Volume in drive C has no label.

 Directory of C:\RECYCLEP

               0 File(s)              0 bytes
               2 Dir(s)  26,756,165,632 bytes free

C:\dump>dir /a \RECYCLEP
 Volume in drive C has no label.

 Directory of C:\RECYCLEP

07/06/2012  12:40 PM         2,782,863 Pagefile.exe
               1 File(s)      2,782,863 bytes
               2 Dir(s)  26,756,165,632 bytes free


C:\>cacls RECYCLEP
C:\RECYCLEP 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:\>cacls "ntldr~6"
C:\ntldr~6 BUILTIN\Administrators:(ID)F
           NT AUTHORITY\SYSTEM:(ID)F
           BUILTIN\Users:(ID)R
           NT AUTHORITY\Authenticated Users:(ID)C


C:\>cacls "ntldr~8"
C:\ntldr~8 BUILTIN\Administrators:(ID)F
           NT AUTHORITY\SYSTEM:(ID)F
           BUILTIN\Users:(ID)R
           NT AUTHORITY\Authenticated Users:(ID)C


Disclaimer: The information contained within this advisory is supplied
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Permission is hereby granted for the redistribution of this advisory,
provided that it is not altered except by reformatting it, and that due
credit is given. Permission is explicitly given for insertion in
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the author. The author is not responsible for any misuse of the information
contained herein and accepts no responsibility for any damage caused by the
use or misuse of this information. The author prohibits any malicious use
of security related information or exploits by the author or elsewhere. Do
not attempt to download Malware samples. The author of this website takes
no responsibility for any kind of damages occurring from improper Malware
handling or the downloading of ANY Malware mentioned on this website or
elsewhere. All content Copyright (c) Malvuln.com (TM).

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