CVE-2016-6423 in IOS
Summary
by MITRE
The IKEv2 client and initiator implementations in Cisco IOS 15.5(3)M and IOS XE allow remote IKEv2 servers to cause a denial of service (device reload) via crafted IKEv2 packets, aka Bug ID CSCux97540.
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Analysis
by VulDB Data Team • 09/24/2024
The vulnerability identified as CVE-2016-6423 represents a critical denial of service flaw affecting Cisco IOS 15.5(3)M and IOS XE implementations of the Internet Key Exchange version 2 protocol. This issue specifically impacts the IKEv2 client and initiator components that handle secure key exchange operations for virtual private networks. The vulnerability stems from insufficient input validation within the IKEv2 processing logic, where crafted malicious packets can trigger unexpected behavior in the network device's processing stack. The flaw allows remote attackers positioned as IKEv2 servers to exploit this weakness without requiring authentication or prior access to the network infrastructure. When properly crafted malicious IKEv2 packets are received by the vulnerable device, they cause the system to enter an unrecoverable state leading to complete device reload and service disruption.
The technical nature of this vulnerability aligns with CWE-129, which describes improper validation of input boundaries, and CWE-248, which covers exposure of unintended executable code. The implementation flaw occurs during the parsing and processing of IKEv2 protocol messages where the device fails to properly validate packet structures and contents before attempting to process them. This creates a condition where malformed or specially crafted IKEv2 packets can cause memory corruption or stack overflow conditions within the device's IKEv2 processing module. The vulnerability is particularly concerning because IKEv2 is a critical protocol used for establishing secure communications between network devices, and the denial of service impact can effectively shut down network connectivity for all services relying on IPsec tunneling.
The operational impact of CVE-2016-6423 extends beyond simple service interruption to potentially compromise network availability and business continuity. Network administrators who rely on IPsec-based VPN connections for remote access, site-to-site connectivity, or secure communications between network segments face significant risk when their devices are vulnerable to this attack. The automatic device reload triggered by the vulnerability means that network services are immediately disrupted without any opportunity for graceful shutdown or failover procedures. This can result in cascading failures across interconnected systems that depend on the affected device for network connectivity, particularly in enterprise environments where multiple network services rely on secure communication channels established through IKEv2. The remote nature of the attack means that adversaries can exploit this vulnerability from anywhere on the internet without requiring physical access or network presence.
Mitigation strategies for this vulnerability should include immediate deployment of Cisco's security patches and software updates addressing the specific IKEv2 processing flaw. Network administrators should implement network segmentation to limit exposure of vulnerable devices to untrusted networks and consider disabling IKEv2 functionality on affected systems until proper patches are applied. The implementation of intrusion detection systems capable of identifying and blocking malicious IKEv2 packets can provide additional protection layers. Organizations should also review their network access controls to ensure that only authorized entities can initiate IKEv2 connections to network devices. This vulnerability demonstrates the importance of maintaining up-to-date network device firmware and implementing comprehensive security monitoring procedures. The ATT&CK framework categorizes this type of vulnerability under privilege escalation and denial of service tactics, highlighting the need for layered security approaches that include both preventive measures and detection capabilities to protect against such exploits.