CVE-2020-3496 in Smart Switch
Summary
by MITRE
A vulnerability in the IPv6 packet processing engine of Cisco Small Business Smart and Managed Switches could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to insufficient validation of incoming IPv6 traffic. An attacker could exploit this vulnerability by sending a crafted IPv6 packet through an affected device. A successful exploit could allow the attacker to cause the switch management CLI to stop responding, resulting in a DoS condition. This vulnerability is specific to IPv6 traffic. IPv4 traffic is not affected.
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Analysis
by VulDB Data Team • 11/10/2020
This vulnerability resides within the IPv6 packet processing engine of Cisco Small Business Smart and Managed Switches, representing a critical flaw in network infrastructure security. The vulnerability stems from inadequate validation mechanisms within the switch's IPv6 handling capabilities, specifically affecting devices that process IPv6 traffic. The flaw manifests when the switch fails to properly validate incoming IPv6 packets, creating an opportunity for malicious actors to manipulate the device's operational state. This represents a fundamental breakdown in the switch's network protocol handling, where the device's inability to properly process malformed or crafted IPv6 packets leads to system instability. The vulnerability is particularly concerning as it affects Cisco's Small Business product line, which often serves as critical network infrastructure in small to medium enterprises where robust security controls may be lacking.
The technical exploitation of this vulnerability occurs through the transmission of specifically crafted IPv6 packets to an affected switch device. Attackers can leverage this flaw by sending malformed IPv6 traffic that triggers an improper response within the switch's management command-line interface. The crafted packets exploit the insufficient validation mechanisms by presenting data structures or packet formats that the switch's IPv6 engine cannot properly handle, leading to a complete system freeze or crash of the management interface. This results in a denial of service condition where network administrators lose access to the switch's management capabilities, effectively rendering the device administratively unreachable. The vulnerability is specifically scoped to IPv6 traffic processing, meaning that IPv4 traffic remains unaffected, though this does not mitigate the overall risk to network operations since IPv6 support is increasingly common in modern network environments.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise network availability and business continuity. When the switch management CLI becomes unresponsive, network administrators lose the ability to monitor, configure, or troubleshoot the affected device, which can cascade into broader network issues. The DoS condition affects the switch's ability to process normal network traffic, as the device may become unresponsive to legitimate network operations while simultaneously failing to handle management requests. This vulnerability particularly impacts small business networks where such devices may serve as core network infrastructure components, and the loss of management access can severely hamper incident response capabilities. The remote nature of the exploit means that attackers can target these devices from outside the network perimeter, making the vulnerability particularly dangerous in environments where network segmentation is not properly implemented.
Mitigation strategies for this vulnerability should focus on implementing network segmentation and access control measures to limit exposure to untrusted networks. Organizations should consider disabling IPv6 functionality on affected switches if the protocol is not required for operations, though this may impact network functionality in environments that depend on IPv6. Network administrators should implement monitoring solutions to detect unusual traffic patterns that might indicate exploitation attempts, as the vulnerability can be triggered by automated scanning tools. Cisco has released patches and software updates to address this vulnerability, and organizations should prioritize applying these updates to affected devices. The vulnerability aligns with CWE-119, which addresses memory corruption vulnerabilities, and represents a classic example of insufficient input validation that can lead to system instability. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique for network denial of service, and the T1071.004 sub-technique for application layer protocol usage. Regular network security assessments and vulnerability scanning should include verification of IPv6 processing capabilities on network infrastructure devices to prevent exploitation of similar vulnerabilities.