CVE-2018-0227 in ASA
Summary
by MITRE
A vulnerability in the Secure Sockets Layer (SSL) Virtual Private Network (VPN) Client Certificate Authentication feature for Cisco Adaptive Security Appliance (ASA) could allow an unauthenticated, remote attacker to establish an SSL VPN connection and bypass certain SSL certificate verification steps. The vulnerability is due to incorrect verification of the SSL Client Certificate. An attacker could exploit this vulnerability by connecting to the ASA VPN without a proper private key and certificate pair. A successful exploit could allow the attacker to establish an SSL VPN connection to the ASA when the connection should have been rejected. This vulnerability affects Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) Software that is running on the following Cisco products: 3000 Series Industrial Security Appliances (ISA), ASA 5500 Series Adaptive Security Appliances, ASA 5500-X Series Next-Generation Firewalls, ASA Services Module for Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers, Adaptive Security Virtual Appliances (ASAv), Firepower 4110 Security Appliances, Firepower 9300 ASA Security Modules. Cisco Bug IDs: CSCvg40155.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 03/03/2023
The vulnerability identified as CVE-2018-0227 represents a critical weakness in the SSL VPN client certificate authentication mechanism of Cisco Adaptive Security Appliances. This flaw resides within the SSL Virtual Private Network client certificate verification process, where the system fails to properly validate the authenticity of client certificates presented during SSL VPN connections. The vulnerability specifically affects the certificate verification logic that should ensure proper authentication through valid private key and certificate pair combinations, creating a pathway for unauthorized access to network resources.
The technical exploitation of this vulnerability occurs when an unauthenticated remote attacker can establish an SSL VPN connection without possessing the legitimate private key and certificate pair required for proper authentication. This represents a fundamental failure in the certificate validation process where the system accepts connections even when the client certificate verification fails to confirm proper cryptographic authentication. The flaw essentially allows attackers to bypass the normal certificate verification steps that should prevent unauthorized access to the network infrastructure, making it particularly dangerous for organizations relying on SSL VPN for secure remote access.
The operational impact of this vulnerability extends across multiple Cisco security products including the 3000 Series Industrial Security Appliances, various ASA 5500 Series appliances, next-generation firewalls, and Firepower threat defense systems. This widespread affected product portfolio means that organizations using these security appliances face significant risk of unauthorized network access, potentially allowing attackers to gain persistent access to sensitive corporate networks. The vulnerability undermines the core security premise of SSL VPN implementations, which rely on strong client authentication to prevent unauthorized access to protected resources.
Organizations affected by this vulnerability should immediately implement mitigation strategies including updating to patched versions of Cisco ASA and FTD software, configuring additional authentication layers, and monitoring network access logs for suspicious activity. The vulnerability aligns with CWE-295, which addresses improper certificate validation, and maps to ATT&CK technique T1078 for valid accounts and T1566 for credential harvesting. Network administrators should also consider implementing additional security controls such as multi-factor authentication, network segmentation, and enhanced monitoring to reduce the attack surface and detect potential exploitation attempts. Cisco has documented this vulnerability in Bug ID CSCvg40155 and recommends immediate remediation to prevent unauthorized access to network resources.