CVE-2005-0943 in VPN 3000 Concentrator
Summary
by MITRE
Cisco VPN 3000 series Concentrator running firmware 4.1.7.A and earlier allows remote attackers to cause a denial of service (device reload or drop user connection) via a crafted HTTPS packet.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 07/02/2019
The vulnerability identified as CVE-2005-0943 affects Cisco VPN 3000 series Concentrators operating with firmware versions 4.1.7.A and earlier, representing a significant security flaw that enables remote attackers to execute denial of service attacks against these network infrastructure devices. This vulnerability specifically targets the HTTPS processing functionality of the concentrator, demonstrating how improperly validated network protocols can be exploited to disrupt critical network services. The affected devices operate as essential components in enterprise network security architectures, serving as gateways for remote access and site-to-site VPN connections that facilitate secure communications between distributed network segments.
The technical flaw manifests through a crafted HTTPS packet that, when processed by the vulnerable concentrator firmware, triggers an unexpected behavior leading to device reload or user connection termination. This represents a classic buffer overflow or input validation vulnerability where the device fails to properly handle malformed or specially constructed HTTPS traffic. The vulnerability operates at the application layer of the network stack, specifically within the secure shell or web interface processing components that handle HTTPS requests from remote clients. According to CWE classification, this vulnerability aligns with CWE-129, Input Validation, and CWE-20, Improper Input Validation, as the device does not adequately validate incoming HTTPS packet structures before processing them. The attack vector requires only network access to the device's HTTPS interface, making it particularly dangerous as it can be exploited from external networks without requiring physical access or authentication credentials.
The operational impact of this vulnerability extends beyond simple service disruption, potentially compromising enterprise network security posture and business continuity operations. When a Cisco VPN 3000 concentrator experiences a reload or user disconnection, it creates immediate gaps in network security coverage that attackers can exploit to gain unauthorized access to protected network segments. The device's role as a primary gateway for remote workers and branch office connections means that a successful attack can effectively cut off legitimate users from accessing corporate resources, potentially causing significant operational disruption. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, Network Denial of Service, and T1566.001, Phishing, as attackers may use this vulnerability as part of broader attack campaigns. The vulnerability also represents a critical weakness in the device's resilience against adversarial network traffic, particularly concerning the device's ability to maintain stable operation under malicious input conditions.
Mitigation strategies for this vulnerability require immediate firmware updates to versions that address the HTTPS processing flaw, as Cisco has released patches specifically designed to resolve this issue. Network administrators should implement network segmentation to limit access to the vulnerable HTTPS interface and deploy intrusion detection systems to monitor for suspicious HTTPS traffic patterns that may indicate exploitation attempts. Additionally, implementing rate limiting and connection monitoring on the HTTPS interface can help detect and prevent exploitation attempts. The vulnerability highlights the importance of maintaining up-to-date network security infrastructure and demonstrates how seemingly minor protocol processing flaws can have significant operational consequences. Organizations should also consider implementing redundant VPN concentrator configurations to maintain network availability during patching operations and ensure that security updates are applied promptly across all network infrastructure components to prevent similar vulnerabilities from compromising enterprise security posture.