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TROJAN:WIN32/ALYAK.B / Remote Stack Corruption

CVE Category Price Severity
N/A CWE-119 Not specified High
Author Risk Exploitation Type Date
Unknown High Remote 2021-01-04
CVSS EPSS EPSSP
CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N 0.021716 0.5032

CVSS vector description

Our sensors found this exploit at: https://cxsecurity.com/ascii/WLB-2021010008

Below is a copy:

TROJAN:WIN32/ALYAK.B / Remote Stack Corruption
Discovery / credits: malvuln - Malvuln.com (c) 2021
Original source: http://malvuln.com/advisory/6547f34243104ba6e21154ad96b799a5.txt
Contact: [email protected]
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
[+] Download advisory


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


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