Nmap vnc-brute NSE Script


This page contains detailed information about how to use the vnc-brute NSE script. For list of all NSE scripts, visit the Nmap NSE Library.

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Overview
Error Messages

Script Overview

Script source code: https://github.com/nmap/nmap/tree/master/scripts/vnc-brute.nse
Script categories: intrusive, brute
Target service / protocol: vnc, tcp
Target network port(s): 5901
List of CVEs: -

Script Description

The vnc-brute.nse script performs brute force password auditing against VNC servers.

Vnc-brute NSE Script Arguments

This is a full list of arguments supported by the vnc-brute.nse script:

vnc-brute.bruteusers

If set, allows the script to iterate over usernames for auth types that require it (plain, Apple Remote Desktop (30), SASL (not supported), and ATEN) Default: false, since most VNC auth types are password-only.

creds.global

Credentials to be returned by Credentials.getCredentials regardless of the service.

creds.[service]

Credentials to be returned by Credentials.getCredentials for [service]. E.g. creds.http=admin:password

passdb

The filename of an alternate password database. Default: nselib/data/passwords.lst

unpwdb.passlimit

The maximum number of passwords passwords will return (default unlimited).

unpwdb.timelimit

The maximum amount of time that any iterator will run before stopping. The value is in seconds by default and you can follow it with ms, s, m, or h for milliseconds, seconds, minutes, or hours. For example, unpwdb.timelimit=30m or unpwdb.timelimit=.5h for 30 minutes. The default depends on the timing template level (see the module description). Use the value 0 to disable the time limit.

unpwdb.userlimit

The maximum number of usernames usernames will return (default unlimited).

userdb

The filename of an alternate username database. Default: nselib/data/usernames.lst

brute.credfile

A file containing username and password pairs delimited by '/'

brute.delay

The number of seconds to wait between guesses (default: 0)

brute.emptypass

Guess an empty password for each user (default: false)

brute.firstonly

Stop guessing after first password is found (default: false)

brute.guesses

The number of guesses to perform against each account. (default: 0 (unlimited)). The argument can be used to prevent account lockouts.

brute.mode

Can be user, pass or creds and determines what mode to run the engine in.

  • user - the unpwdb library is used to guess passwords, every password Password is tried for each user. (The user iterator is in the outer loop)
  • pass - the unpwdb library is used to guess passwords, each password Is tried for every user. (The password iterator is in the outer loop)
  • creds - a set of credentials (username and password pairs) are Guessed against the service. This allows for lists of known or common username and password combinations to be tested. If no mode is specified and the script has not added any custom iterator the pass mode will be enabled.

brute.passonly

Iterate over passwords only for services that provide only a password for authentication. (default: false)

brute.retries

The number of times to retry if recoverable failures occur. (default: 2)

brute.start

The number of threads the engine will start with. (default: 5).

brute.threads

The number of initial worker threads, the number of active threads will be automatically adjusted.

brute.unique

Make sure that each password is only guessed once (default: true)

brute.useraspass

Guess the username as password for each user (default: true)

creds.[service]

Credentials to be returned by Credentials.getCredentials for [service]. E.g. creds.http=admin:password

- - -
To use these script arguments, add them to the Nmap command line using the --script-args arg1=value,[arg2=value,..] syntax. For example:

nmap --script=vnc-brute --script-args vnc-brute.bruteusers=value,creds.global=value <target>

Vnc-brute NSE Script Example Usage

Here's an example of how to use the vnc-brute.nse script:

nmap --script vnc-brute -p 5900 <host>

Vnc-brute NSE Script Example Output

Here's a sample output from the vnc-brute.nse script:

PORT     STATE  SERVICE REASON
5900/tcp open   vnc     syn-ack
| vnc-brute:
|   Accounts
|_    123456 => Valid credentials

Vnc-brute NSE Script Example XML Output

There is no sample XML output for this module. However, by providing the -oX <file> option, Nmap will produce a XML output and save it in the file.xml file.

Author

  • Patrik Karlsson

References

See Also

Related NSE scripts to the vnc-brute.nse script:

Visit Nmap NSE Library for more scripts.

The vnc-brute.nse script may fail with the following error messages. Check for the possible causes by using the code snippets highlighted below found in the script source code. This can often times help in identifying the root cause of the problem.

VNC handshake failed

Here is a relevant code snippet related to the "VNC handshake failed" error message:

75:	      data:match("Your connection has been rejected.") ) ) then
76:	      local err = brute.Error:new( data )
77:	      err:setAbort( true )
78:	      return false, err
79:	    elseif ( not(status) ) then
80:	      local err = brute.Error:new( "VNC handshake failed" )
81:	      -- This might be temporary, set the retry flag
82:	      err:setRetry( true )
83:	      return false, err
84:	    end
85:

Authentication failed

Here is a relevant code snippet related to the "Authentication failed" error message:

85:	
86:	    status, data = self.vnc:login( username, password )
87:	
88:	    if ( status ) then
89:	      return true, creds.Account:new(username, password, creds.State.VALID)
90:	    elseif ( not( data:match("Authentication failed") ) ) then
91:	      local err = brute.Error:new( data )
92:	      -- This might be temporary, set the retry flag
93:	      err:setRetry( true )
94:	      return false, err
95:	    end

Incorrect password

Here is a relevant code snippet related to the "Incorrect password" error message:

92:	      -- This might be temporary, set the retry flag
93:	      err:setRetry( true )
94:	      return false, err
95:	    end
96:	
97:	    return false, brute.Error:new( "Incorrect password" )
98:	
99:	  end,
100:	
101:	  disconnect = function( self )
102:	    self.vnc:disconnect()

No authentication required

Here is a relevant code snippet related to the "No authentication required" error message:

115:	    if ( not(status) ) then
116:	      return stdnse.format_output( false, data )
117:	    end
118:	
119:	    if ( vnc:supportsSecType(vnc.sectypes.NONE) ) then
120:	      return false, "No authentication required"
121:	    end
122:	
123:	    status, data = vnc:login( nil, "is_sec_mec_supported?" )
124:	    -- Check whether auth succeeded. This is most likely because one of the
125:	    -- NONE auth types was supported, since vnc.lua will just return true in that case.

No authentication required

Here is a relevant code snippet related to the "No authentication required" error message:

122:	
123:	    status, data = vnc:login( nil, "is_sec_mec_supported?" )
124:	    -- Check whether auth succeeded. This is most likely because one of the
125:	    -- NONE auth types was supported, since vnc.lua will just return true in that case.
126:	    if status then
127:	      return false, "No authentication required"
128:	    end
129:	
130:	    if ( data:match("The server does not support.*security type") ) then
131:	      return stdnse.format_output( false, "  \n  " .. data )
132:	    end

n

Here is a relevant code snippet related to the " n " error message:

126:	    if status then
127:	      return false, "No authentication required"
128:	    end
129:	
130:	    if ( data:match("The server does not support.*security type") ) then
131:	      return stdnse.format_output( false, "  \n  " .. data )
132:	    end
133:	
134:	    return true
135:	  end,
136:

Version

This page has been created based on Nmap version 7.92.

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