CVE-2015-0632 in IOS
Summary
by MITRE
Race condition in the Neighbor Discovery (ND) protocol implementation in Cisco IOS and IOS XE allows remote attackers to cause a denial of service via a flood of Router Solicitation messages on the local network, aka Bug ID CSCuo67770.
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Analysis
by VulDB Data Team • 06/21/2017
The vulnerability described in CVE-2015-0632 represents a critical race condition within the Neighbor Discovery protocol implementation of Cisco IOS and IOS XE operating systems. This flaw specifically affects the handling of Router Solicitation messages within the IPv6 networking stack, creating a pathway for remote attackers to exploit the system's response mechanisms. The issue manifests as a denial of service condition that can be triggered through network-based attacks, making it particularly dangerous in environments where network availability is critical. The vulnerability was identified and documented under Cisco Bug ID CSCuo67770, highlighting the specific implementation weakness in the router's IPv6 processing capabilities.
The technical root cause of this vulnerability lies in the improper synchronization of network processing routines when handling Router Solicitation messages. During normal operation, routers implement the Neighbor Discovery protocol to maintain network connectivity and routing information. However, the race condition occurs when multiple Router Solicitation messages are processed concurrently without proper locking mechanisms or state validation. This allows attackers to flood the system with carefully crafted solicitation packets that exploit timing dependencies in the processing logic. When the system attempts to respond to these messages, the race condition causes unpredictable behavior in the routing table maintenance and neighbor cache management functions, ultimately leading to system instability or complete service disruption.
The operational impact of this vulnerability extends beyond simple network disruption, as it can affect critical infrastructure components that rely on stable IPv6 connectivity. Attackers can leverage this weakness to create sustained denial of service conditions that may persist until the affected device is manually restarted or the system is rebooted. The remote nature of the attack means that adversaries do not require physical access or network credentials to exploit the vulnerability, making it particularly dangerous in enterprise environments. Network administrators may observe degraded performance, intermittent connectivity issues, or complete network outages as the system struggles to process the flood of malicious Router Solicitation messages. This vulnerability particularly affects routers and network devices that are configured to operate in IPv6 environments, where the Neighbor Discovery protocol is actively utilized.
Mitigation strategies for CVE-2015-0632 should focus on both immediate defensive measures and long-term architectural improvements. Cisco has released patches and software updates to address this specific race condition in their IOS and IOS XE implementations, which should be deployed immediately on affected systems. Network administrators should implement rate limiting mechanisms to control the volume of Router Solicitation messages that can be processed within a given time period. Additionally, implementing access control lists and firewall rules to filter suspicious Router Solicitation traffic can provide an additional layer of protection. The vulnerability aligns with CWE-362, which describes race conditions in software implementations, and can be mapped to ATT&CK technique T1498 for denial of service attacks. Organizations should also consider implementing network monitoring solutions that can detect unusual patterns of Router Solicitation messages and automatically trigger alerts or defensive responses. Regular security assessments and vulnerability scanning should be conducted to identify any remaining instances of this vulnerability across the network infrastructure.