CVE-2018-0273 in ASR 5000
Summary
by MITRE
A vulnerability in the IPsec Manager of Cisco StarOS for Cisco Aggregation Services Router (ASR) 5000 Series Routers and Virtualized Packet Core (VPC) System Software could allow an unauthenticated, remote attacker to terminate all active IPsec VPN tunnels and prevent new tunnels from being established, resulting in a denial of service (DoS) condition. The vulnerability is due to improper processing of corrupted Internet Key Exchange Version 2 (IKEv2) messages. An attacker could exploit this vulnerability by sending crafted IKEv2 messages toward an affected router. A successful exploit could allow the attacker to cause the ipsecmgr service to reload. A reload of this service could cause all IPsec VPN tunnels to be terminated and prevent new tunnels from being established until the service has restarted, resulting in a DoS condition. This vulnerability affects the following Cisco products when they are running Cisco StarOS: Cisco Aggregation Services Router (ASR) 5000 Series Routers, Virtualized Packet Core (VPC) System Software. Cisco Bug IDs: CSCve29605.
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Analysis
by VulDB Data Team • 03/03/2023
The vulnerability described in CVE-2018-0273 represents a critical denial of service weakness within Cisco StarOS operating systems that governs the IPsec Manager functionality of network infrastructure devices. This flaw specifically targets the Internet Key Exchange Version 2 protocol implementation within Cisco Aggregation Services Router 5000 Series and Virtualized Packet Core systems, creating a scenario where unauthorized remote actors can disrupt network security communications. The issue stems from inadequate validation mechanisms within the IKEv2 message processing pipeline, which fails to properly handle malformed or corrupted packets that should be rejected during normal protocol operations. The vulnerability affects a significant portion of Cisco's enterprise networking portfolio, particularly those deployments utilizing StarOS software for managing secure communications through IPsec tunnels.
The technical exploitation of this vulnerability occurs through the deliberate crafting of malicious IKEv2 messages that trigger memory corruption or state management failures within the ipsecmgr service component. When the affected system processes these malformed packets, the improper input handling causes the service to crash and subsequently reload automatically, leading to complete disruption of IPsec tunnel operations. This behavior constitutes a direct violation of the secure communication protocols that IPsec tunnels are designed to maintain, as the system cannot distinguish between legitimate protocol traffic and maliciously crafted packets that exploit the parsing weakness. The vulnerability's impact is particularly severe because IPsec tunnels form the backbone of secure remote access and site-to-site connectivity in enterprise networks, making this DoS condition potentially devastating to business continuity and network availability.
From an operational perspective, this vulnerability creates a substantial risk for organizations relying on Cisco ASR 5000 Series routers and VPC systems for their network security infrastructure. The automatic service reload process means that network administrators have no opportunity to intervene or mitigate the attack, as the system responds to the malicious input by immediately terminating all active tunnels and preventing new connections. This behavior directly violates the principle of network resilience and availability that organizations expect from their security infrastructure. The attack vector requires minimal sophistication from the adversary, as it only requires sending specific malformed IKEv2 packets to the target device, making it particularly dangerous for environments where such devices are exposed to untrusted network traffic. The vulnerability's classification aligns with CWE-129, which addresses improper validation of input boundaries, and can be mapped to ATT&CK technique T1499.002, which covers network disruption through denial of service attacks.
Organizations affected by this vulnerability should implement immediate mitigations including network segmentation to isolate critical ASR 5000 devices from untrusted networks, deployment of access control lists to filter IKEv2 traffic, and application of Cisco's official security patches. The recommended approach involves configuring the affected devices to reject malformed IKEv2 messages before they reach the ipsecmgr service, effectively creating a protective barrier against the specific exploit vectors. Additionally, network monitoring should be enhanced to detect unusual patterns of IKEv2 traffic that may indicate attempted exploitation, while regular security audits should verify that the mitigation measures remain effective against evolving attack techniques. The vulnerability demonstrates the critical importance of proper input validation in security-critical network services and highlights the necessity of maintaining up-to-date security patches for enterprise networking infrastructure.