CVE-2005-1802 in VPN Router
Summary
by MITRE
Nortel VPN Router (aka Contivity) allows remote attackers to cause a denial of service (crash) via an IPsec IKE packet with a malformed ISAKMP header.
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Analysis
by VulDB Data Team • 07/03/2019
The vulnerability identified as CVE-2005-1802 affects Nortel VPN routers, specifically those running the Contivity firmware, and represents a critical denial of service weakness that can be exploited remotely. This issue manifests when the affected device receives an IPsec IKE packet containing a malformed ISAKMP header, leading to system instability and potential complete service disruption. The vulnerability resides within the router's IPsec implementation and demonstrates a fundamental flaw in packet validation and error handling mechanisms.
The technical flaw stems from inadequate input validation within the ISAKMP (Internet Security Association and Key Management Protocol) processing component of the Contivity VPN router. When the device encounters an IPsec IKE packet with malformed ISAKMP headers, the router's processing logic fails to properly handle the unexpected packet structure, resulting in a system crash or reboot. This represents a classic buffer overflow or parsing error scenario where the device does not implement proper bounds checking or error recovery procedures for malformed network traffic. The vulnerability is particularly concerning because it can be triggered remotely without requiring authentication, making it an attractive target for malicious actors seeking to disrupt network services.
The operational impact of this vulnerability extends beyond simple service interruption, as it can result in complete network availability loss for organizations relying on these VPN routers for secure communications. When exploited successfully, the denial of service condition can persist until manual intervention occurs, requiring administrators to physically access the device or perform remote reboot procedures. This vulnerability directly affects network infrastructure reliability and can have cascading effects on business continuity, especially in environments where remote access is critical for business operations. The attack surface is particularly wide since the vulnerability can be exploited from any location with network access to the affected router's IPsec service ports.
Organizations should implement immediate mitigations including network segmentation to isolate affected devices, deployment of intrusion detection systems to monitor for malformed IKE packets, and application of vendor-provided patches or firmware updates. The vulnerability aligns with CWE-129, which covers improper validation of input boundaries, and can be categorized under ATT&CK technique T1498, which involves network denial of service attacks. Network administrators should also consider implementing rate limiting on IPsec IKE traffic and configuring firewall rules to restrict access to the affected service ports. Regular network monitoring and vulnerability assessments are essential to identify similar weaknesses in other network infrastructure components and to maintain overall security posture.