CVE-2015-6415 in Unified Computing System
Summary
by MITRE
Cisco Unified Computing System (UCS) 2.2(3f)A on Fabric Interconnect 6200 devices allows remote attackers to cause a denial of service (CPU consumption or device outage) via a SYN flood on the SSH port during the booting process, aka Bug ID CSCuu81757.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 07/01/2022
The vulnerability described in CVE-2015-6415 represents a critical denial of service weakness within Cisco Unified Computing System components, specifically affecting Fabric Interconnect 6200 devices running UCS version 2.2(3f)A. This flaw manifests during the device booting process when the system becomes susceptible to SYN flood attacks targeting the Secure Shell port, leading to either excessive cpu utilization or complete device outage. The vulnerability is particularly concerning as it occurs during the critical boot phase when the system is most vulnerable and least protected against malicious network traffic patterns.
The technical implementation of this vulnerability stems from inadequate handling of TCP connection requests during the early boot stages of the Fabric Interconnect device. When a SYN flood attack is initiated against the SSH port, the system's TCP stack fails to properly manage the excessive connection requests, causing the device to consume disproportionate cpu resources in processing these malformed or malicious connection attempts. This behavior aligns with common network protocol vulnerabilities where insufficient rate limiting or connection queue management allows attackers to exhaust system resources through legitimate protocol mechanisms. The flaw essentially creates a resource exhaustion condition that prevents the device from completing its normal boot process or maintaining operational stability.
The operational impact of CVE-2015-6415 extends beyond simple service disruption to encompass complete system unavailability and potential business continuity issues within data center environments. Organizations relying on Cisco UCS infrastructure for critical computing operations face significant risk when this vulnerability is exploited, as the device outage can affect multiple virtualized workloads and network services dependent on the fabric interconnect. The timing during the boot process makes this attack particularly devastating since it prevents system recovery and can lead to extended downtime requiring manual intervention and potentially hardware replacement. This vulnerability directly impacts the availability and reliability of enterprise computing infrastructure, potentially affecting service level agreements and operational efficiency.
Mitigation strategies for this vulnerability should include implementing network-level protections such as rate limiting and SYN cookies to prevent the exploitation of TCP connection handling weaknesses. Organizations should also consider deploying intrusion detection systems that can identify and block SYN flood patterns targeting the affected SSH ports. The most effective long-term solution involves applying the official Cisco security patches and updates that address the specific resource management issues in the TCP stack implementation. Network administrators should also implement monitoring protocols to detect unusual cpu utilization patterns that may indicate exploitation attempts, as outlined in the ATT&CK framework's network denial of service tactics. Additionally, organizations should consider network segmentation strategies to limit exposure of critical infrastructure components to untrusted networks and implement proper access controls to minimize the attack surface. This vulnerability highlights the importance of robust resource management in embedded systems and the necessity of implementing proper protocol handling mechanisms to prevent resource exhaustion attacks.