CVE-2002-1102 in VPN 3000 Concentrator
Summary
by MITRE
The LAN-to-LAN IPSEC capability for Cisco VPN 3000 Concentrator 2.2.x, and 3.x before 3.5.4, allows remote attackers to cause a denial of service via an incoming LAN-to-LAN connection with an existing security association with another device on the remote network, which causes the concentrator to remove the previous connection.
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Analysis
by VulDB Data Team • 05/16/2019
The vulnerability identified as CVE-2002-1102 affects Cisco VPN 3000 Concentrator devices running software versions 2.2.x and 3.x prior to 3.5.4. This issue specifically impacts the LAN-to-LAN IPsec capability which is a critical feature enabling secure communication between different network segments across the internet. The vulnerability resides in how the concentrator handles incoming LAN-to-LAN connections when existing security associations already exist with other devices on remote networks, creating a scenario where the device's connection management logic fails to properly handle concurrent security associations.
The technical flaw manifests when an attacker establishes a LAN-to-LAN connection to the vulnerable concentrator while another active security association exists with a different remote device. This specific interaction triggers a denial of service condition where the concentrator's processing logic incorrectly removes the existing valid connection in favor of the new incoming connection. This behavior represents a fundamental flaw in the IPsec security association management and connection handling mechanisms within the Cisco VPN 3000 Concentrator software. The vulnerability is classified under CWE-121 as a buffer overflow condition, though more specifically relates to improper handling of security associations in network security protocols.
The operational impact of this vulnerability is significant for organizations relying on Cisco VPN 3000 Concentrators for secure network communications. When exploited, the vulnerability can cause legitimate network connections to be abruptly terminated, leading to service disruption and potential loss of network connectivity for authorized users. This denial of service condition can be particularly damaging in enterprise environments where continuous network availability is critical for business operations, as it can effectively render parts of the network inaccessible to legitimate users while the device recovers from the malformed connection handling.
Organizations affected by this vulnerability should immediately implement mitigations including upgrading to Cisco VPN 3000 Concentrator software version 3.5.4 or later, which contains the necessary patches to address the security association handling issue. Network administrators should also consider implementing additional monitoring and alerting mechanisms to detect unusual connection patterns that might indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1499.004 which involves network disruption through denial of service attacks, making it a critical concern for network security teams. Additionally, implementing proper access controls and limiting exposure of the vulnerable concentrator to untrusted networks can help reduce the attack surface while permanent patches are deployed. Organizations should also verify their current software versions and ensure all devices are running patched firmware to prevent exploitation of this vulnerability.