CVE-2005-2025 in VPN 3000 Concentrator
Summary
by MITRE
Cisco VPN 3000 Concentrator before 4.1.7.F allows remote attackers to determine valid groupnames by sending an IKE Aggressive Mode packet with the groupname in the ID field, which generates a response if the groupname is valid, but does not generate a response for an invalid groupname.
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Analysis
by VulDB Data Team • 06/07/2019
The vulnerability identified as CVE-2005-2025 affects Cisco VPN 3000 Concentrator devices running firmware versions prior to 4.1.7.F, representing a significant information disclosure weakness that undermines the security of virtual private network implementations. This flaw operates within the Internet Key Exchange protocol framework, specifically targeting the aggressive mode negotiation process that establishes secure communications between VPN clients and concentrators. The vulnerability stems from the concentrator's inconsistent response behavior when processing IKE packets, creating a timing-based side-channel attack vector that can be exploited by remote adversaries.
The technical mechanism of this vulnerability involves the concentrator's differential response handling during IKE aggressive mode negotiations. When an attacker sends a malformed IKE packet containing a groupname in the identification field, the system behaves differently based on whether the groupname exists within its configuration. Valid groupnames trigger a response packet containing an error message, while invalid groupnames result in no response at all. This response inconsistency provides attackers with a clear indication of groupname validity, effectively enabling them to perform automated enumeration attacks against the VPN concentrator's groupname database. The flaw directly maps to CWE-200, Information Exposure, and specifically represents a form of information leakage through response timing variations.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables attackers to systematically enumerate valid groupnames within the VPN concentrator's configuration. This enumeration capability significantly reduces the attack surface for subsequent exploitation attempts, as valid groupnames can then be targeted for brute force attacks against associated authentication mechanisms. The vulnerability affects the confidentiality aspect of the CIA triad, as it exposes sensitive configuration information that should remain protected within the organization's security infrastructure. Attackers can leverage this information to craft more sophisticated attacks against the VPN infrastructure, potentially leading to unauthorized access to protected network resources.
Mitigation strategies for this vulnerability require immediate firmware upgrades to Cisco VPN 3000 Concentrator version 4.1.7.F or later, which addresses the inconsistent response behavior in the IKE aggressive mode implementation. Network administrators should also implement additional security controls such as disabling IKE aggressive mode when possible, implementing proper access controls on the VPN concentrator management interfaces, and monitoring for unusual traffic patterns that may indicate enumeration attempts. The vulnerability demonstrates the importance of consistent error handling in security-critical systems, aligning with ATT&CK technique T1212, Exploitation for Credential Access, where information disclosure can facilitate further compromise. Organizations should also consider implementing network segmentation and intrusion detection systems to monitor for potential exploitation attempts targeting this specific vulnerability.