CVE-2017-12237 in IOS
Summary
by MITRE
A vulnerability in the Internet Key Exchange Version 2 (IKEv2) module of Cisco IOS 15.0 through 15.6 and Cisco IOS XE 3.5 through 16.5 could allow an unauthenticated, remote attacker to cause high CPU utilization, traceback messages, or a reload of an affected device that leads to a denial of service (DoS) condition. The vulnerability is due to how an affected device processes certain IKEv2 packets. An attacker could exploit this vulnerability by sending specific IKEv2 packets to an affected device to be processed. A successful exploit could allow the attacker to cause high CPU utilization, traceback messages, or a reload of the affected device that leads to a DoS condition. This vulnerability affects Cisco devices that have the Internet Security Association and Key Management Protocol (ISAKMP) enabled. Although only IKEv2 packets can be used to trigger this vulnerability, devices that are running Cisco IOS Software or Cisco IOS XE Software are vulnerable when ISAKMP is enabled. A device does not need to be configured with any IKEv2-specific features to be vulnerable. Many features use IKEv2, including different types of VPNs such as the following: LAN-to-LAN VPN; Remote-access VPN, excluding SSL VPN; Dynamic Multipoint VPN (DMVPN); and FlexVPN. Cisco Bug IDs: CSCvc41277.
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Analysis
by VulDB Data Team • 09/09/2024
The vulnerability described in CVE-2017-12237 represents a critical denial of service weakness within the Internet Key Exchange Version 2 implementation of Cisco IOS and IOS XE operating systems. This flaw resides in the ISAKMP processing module that handles IKEv2 protocol communications, affecting a broad range of Cisco networking equipment from IOS version 15.0 through 15.6 and IOS XE version 3.5 through 16.5. The vulnerability stems from improper handling of specific IKEv2 packet structures that trigger excessive CPU processing demands within the affected devices. The flaw is particularly concerning because it requires no authentication credentials for exploitation, making it accessible to any remote attacker who can reach the targeted network infrastructure.
The technical execution of this vulnerability involves sending specifically crafted IKEv2 packets to an affected Cisco device, which then processes these malformed packets in a manner that consumes disproportionate system resources. The processing behavior leads to sustained high CPU utilization that can eventually cause system instability and traceback messages indicating internal processing errors. In severe cases, the device may automatically reload its operating system as a protective mechanism, resulting in complete service interruption. This processing anomaly occurs regardless of whether the device has specific IKEv2 configurations enabled, as the vulnerability exists within the core protocol handling mechanisms rather than specific feature implementations.
The operational impact of this vulnerability extends across multiple Cisco VPN implementations that rely on IKEv2 for security association establishment. Any device running affected Cisco software versions that have ISAKMP enabled becomes susceptible to this attack vector, regardless of whether it's configured for specific VPN services. This includes various VPN types such as LAN-to-LAN VPN connections, remote-access VPN implementations, Dynamic Multipoint VPN configurations, and FlexVPN deployments. The broad applicability means that network administrators must consider this vulnerability across their entire infrastructure rather than just specific deployment scenarios, as even devices that appear to be minimally configured may be at risk.
From a cybersecurity framework perspective, this vulnerability aligns with CWE-20 (Improper Input Validation) and represents a classic example of resource exhaustion attack patterns that map to MITRE ATT&CK technique T1499.002 (Endpoint Denial of Service). The vulnerability demonstrates how protocol implementation flaws can create significant operational risks, particularly in enterprise networks where VPN connectivity is essential for business operations. Organizations should implement network segmentation and access controls to limit exposure to this vulnerability, while also applying the appropriate Cisco security patches as recommended in their security advisories. The vulnerability's impact is amplified by the fact that it affects fundamental security protocols rather than specific applications, making it a critical concern for network security teams responsible for maintaining infrastructure availability and integrity.