CVE-2002-1100 in VPN 3000 Concentrator
Summary
by MITRE
Cisco VPN 3000 Concentrator 2.2.x, and 3.x before 3.5.3, allows remote attackers to cause a denial of service (crash) via a long (1) username or (2) password to the HTML login interface.
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Analysis
by VulDB Data Team • 06/09/2019
The vulnerability identified as CVE-2002-1100 affects Cisco VPN 3000 Concentrator appliances running software versions 2.2.x and 3.x prior to 3.5.3. This represents a classic buffer overflow condition that manifests specifically within the HTML login interface of the VPN concentrator. The flaw occurs when remote attackers submit excessively long username or password parameters during the authentication process, causing the system to crash and become unavailable to legitimate users. This vulnerability directly impacts the availability aspect of the CIA triad and can be classified under CWE-121 as a stack-based buffer overflow condition. The attack vector is remote and does not require authentication to exploit, making it particularly dangerous as it can be leveraged by any attacker with network access to the affected system.
The technical implementation of this vulnerability stems from inadequate input validation within the web-based authentication interface of the Cisco VPN concentrator. When the system receives authentication requests containing overly long strings for either username or password fields, the application fails to properly bounds-check the input data before processing it. This lack of proper input sanitization allows the attacker to overwrite adjacent memory locations in the application's stack, ultimately leading to a system crash. The vulnerability is particularly concerning because it affects the core authentication mechanism of the VPN concentrator, which is fundamental to network security operations. The crash occurs during the HTML login processing phase, indicating that the flaw exists in the web server component of the concentrator rather than in lower-level network protocols, making it more accessible to attackers with basic web exploitation knowledge.
The operational impact of CVE-2002-1100 extends beyond simple service disruption as it can severely compromise network security infrastructure. Organizations relying on Cisco VPN 3000 concentrators for remote access and site-to-site connections would experience complete service outages when this vulnerability is exploited, potentially leaving critical network segments inaccessible to authorized personnel. The denial of service condition affects not only the immediate availability of the VPN service but also impacts business continuity and remote work capabilities. In enterprise environments where these concentrators serve as primary gateways for remote access, such an attack could result in significant productivity losses and potential security breaches if attackers use the service disruption as a cover for more sophisticated attacks. The vulnerability's exploitation requires minimal technical skill, making it attractive to a wide range of threat actors from script kiddies to organized groups.
Mitigation strategies for CVE-2002-1100 should prioritize immediate software updates to version 3.5.3 or later, which contain the necessary patches to address the buffer overflow conditions. Network administrators should also implement additional security controls such as rate limiting and connection throttling at the network perimeter to reduce the effectiveness of potential exploitation attempts. The implementation of intrusion detection systems capable of identifying malformed HTTP requests targeting the login interface can provide early warning of exploitation attempts. Organizations should also consider deploying web application firewalls that can filter out overly long input parameters before they reach the vulnerable application components. From a defensive perspective, this vulnerability aligns with ATT&CK technique T1499.004 for network denial of service and demonstrates the importance of input validation controls as outlined in the OWASP Top Ten. Regular vulnerability assessments and security testing should be conducted to identify similar buffer overflow conditions in other network infrastructure components, as this represents a common class of vulnerability that has historically affected many network devices and applications.