CVE-2002-1106 in VPN Client
Summary
by MITRE
Cisco Virtual Private Network (VPN) Client software 2.x.x, and 3.x before 3.5.1C, does not properly verify that certificate DN fields match those of the certificate from the VPN Concentrator, which allows remote attackers to conduct man-in-the-middle attacks.
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Analysis
by VulDB Data Team • 04/19/2019
The vulnerability identified as CVE-2002-1106 represents a critical weakness in Cisco's Virtual Private Network client software versions 2.x.x and 3.x prior to 3.5.1C. This flaw specifically targets the certificate verification process within the VPN authentication mechanism, creating a significant security gap that adversaries can exploit to compromise secure communications. The vulnerability resides in the client-side certificate validation logic where the software fails to properly validate the distinguished name (DN) fields of certificates against the corresponding fields from the VPN concentrator, allowing for potential certificate forgery scenarios.
The technical nature of this vulnerability stems from insufficient certificate validation procedures within the Cisco VPN client implementation. When establishing a secure connection, the client should verify that the certificate presented by the VPN concentrator matches expected parameters including distinguished name components such as organization, location, and other identifying attributes. However, the flawed validation process permits attackers to present certificates with matching serial numbers but different DN fields, effectively bypassing the authentication mechanism. This weakness directly maps to CWE-295 which addresses improper certificate validation and can be categorized under ATT&CK technique T1556.001 for credential harvesting through certificate manipulation.
The operational impact of this vulnerability extends beyond simple authentication bypass, as it enables sophisticated man-in-the-middle attacks that can intercept, modify, or redirect encrypted VPN traffic. Attackers exploiting this vulnerability can establish fraudulent VPN connections that appear legitimate to end users while allowing unauthorized access to corporate networks. The implications are particularly severe in enterprise environments where VPN clients are used for remote access to sensitive systems and data. The vulnerability affects the integrity and confidentiality of communications, potentially exposing sensitive business information, proprietary data, and user credentials to unauthorized parties.
Organizations should implement immediate mitigations including upgrading to Cisco VPN client versions 3.5.1C or later, which contain the necessary certificate validation fixes. Network administrators should also consider implementing additional security controls such as certificate pinning, enhanced monitoring of VPN connection attempts, and regular security assessments of remote access configurations. The vulnerability demonstrates the critical importance of proper certificate validation in cryptographic protocols and highlights the need for robust authentication mechanisms in network security infrastructure. Security teams should review their current VPN client deployments to ensure all systems are updated and monitor for potential exploitation attempts in their network traffic logs.