CVE-2002-1098 in VPN 3000 Concentrator
Summary
by MITRE
Cisco VPN 3000 Concentrator 2.2.x, and 3.x before 3.5.3, adds an "HTTPS on Public Inbound (XML-Auto)(forward/in)" rule but sets the protocol to "ANY" when the XML filter configuration is enabled, which ultimately allows arbitrary traffic to pass through the concentrator.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 05/16/2019
The vulnerability identified as CVE-2002-1098 represents a critical configuration flaw in Cisco VPN 3000 Concentrator software versions 2.2.x and 3.x prior to 3.5.3. This issue stems from improper rule configuration within the XML filter functionality that governs inbound traffic handling. The vulnerability specifically manifests when the XML filter configuration is enabled, creating a security gap that undermines the intended network access controls. The flaw operates at the network filtering layer where access control policies are enforced, making it particularly dangerous for enterprise security infrastructures that rely on proper traffic segmentation and access control.
The technical implementation of this vulnerability involves the creation of an "HTTPS on Public Inbound (XML-Auto)(forward/in)" rule that is incorrectly configured to use the "ANY" protocol setting instead of the more restrictive protocol specification. This misconfiguration effectively nullifies the intended security controls by allowing any type of traffic to pass through the concentrator regardless of the specific protocol requirements. The protocol field in firewall rules serves as a fundamental security mechanism for traffic filtering, and when set to "ANY," it creates an unrestricted pathway that bypasses normal security enforcement points. This configuration error aligns with CWE-284, which addresses improper access control mechanisms, and specifically demonstrates weak privilege management in network security policy enforcement.
The operational impact of this vulnerability is severe for organizations relying on Cisco VPN 3000 Concentrators for secure remote access and network segmentation. Attackers could exploit this flaw to gain unauthorized access to internal network resources by bypassing the intended HTTPS restrictions that should limit traffic to secure web protocols only. The vulnerability essentially creates a backdoor that allows arbitrary traffic to flow through the concentrator, potentially enabling man-in-the-middle attacks, data exfiltration, and lateral movement within the network. This represents a significant escalation from normal network security controls to a state where the device itself becomes a potential entry point for malicious actors. The impact extends beyond simple unauthorized access to include potential complete network compromise, especially when the concentrator serves as a gateway between trusted and untrusted network zones.
Organizations affected by this vulnerability should immediately implement the remediation measures provided by Cisco, including upgrading to version 3.5.3 or later of the VPN 3000 Concentrator software. The upgrade process should include comprehensive review and reconfiguration of all XML filter settings to ensure proper protocol specifications are enforced. Network administrators should also conduct immediate security audits to identify any existing unauthorized access patterns that may have occurred due to this vulnerability. The mitigation strategy aligns with ATT&CK technique T1071.004, which covers application layer protocol: web protocols, as the vulnerability specifically affects web-based access controls. Additionally, organizations should implement network monitoring solutions to detect unusual traffic patterns that might indicate exploitation attempts, and establish baseline network behavior for comparison against potential malicious activity. Regular security assessments and proper configuration management practices should be enforced to prevent similar issues in other network security devices and appliances.