CVE-2021-34780 in Small Business 220
Summary
by MITRE • 10/07/2021
Multiple vulnerabilities exist in the Link Layer Discovery Protocol (LLDP) implementation for Cisco Small Business 220 Series Smart Switches. An unauthenticated, adjacent attacker could perform the following: Execute code on the affected device or cause it to reload unexpectedly Cause LLDP database corruption on the affected device For more information about these vulnerabilities, see the Details section of this advisory. Note: LLDP is a Layer 2 protocol. To exploit these vulnerabilities, an attacker must be in the same broadcast domain as the affected device (Layer 2 adjacent). Cisco has released firmware updates that address these vulnerabilities.
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Analysis
by VulDB Data Team • 10/10/2021
The vulnerability CVE-2021-34780 represents a critical security flaw in the Link Layer Discovery Protocol implementation of Cisco Small Business 220 Series Smart Switches, specifically targeting the Layer 2 network infrastructure components that facilitate device discovery and network topology mapping. This vulnerability classifies under CWE-119 as it involves improper restriction of operations within a memory buffer, allowing for potential code execution and system instability. The attack vector requires an adjacent network position within the same broadcast domain, making it a local privilege escalation threat that leverages the inherent trust relationships established by LLDP protocols. These switches operate at Layer 2, making them particularly susceptible to attacks that exploit the protocol's design assumptions about network adjacency and device trust relationships.
The technical exploitation of this vulnerability occurs through manipulation of LLDP packets that the affected switches process to maintain network topology information and device discovery data. An unauthenticated attacker positioned within the same broadcast domain can craft malicious LLDP frames that trigger buffer overflows or memory corruption within the switch's LLDP implementation, potentially leading to arbitrary code execution or unexpected system reloads. The vulnerability specifically affects the LLDP database management system, where corrupted data structures can cause the switch to malfunction or crash, disrupting network operations and potentially providing a foothold for further attacks. This represents a significant concern for network infrastructure security as it undermines the fundamental trust model that Layer 2 protocols rely upon for network discovery and management.
The operational impact of CVE-2021-34780 extends beyond simple service disruption to potentially compromise the entire network infrastructure that relies on these switches for connectivity management. When exploited, the vulnerability can cause unauthorized code execution on the switch itself, potentially allowing attackers to gain administrative privileges or install persistent backdoors within the network infrastructure. The LLDP database corruption aspect of the vulnerability can lead to incorrect network topology information being distributed throughout the network, causing routing issues, network segmentation problems, and potentially enabling more sophisticated attacks that exploit the confusion in network topology mapping. This vulnerability directly impacts the network's operational integrity and can create conditions that facilitate lateral movement attacks within the network environment.
Organizations should implement immediate mitigations including applying the firmware updates provided by Cisco, which address the specific buffer overflow conditions within the LLDP implementation. Network segmentation strategies should be enhanced to limit the broadcast domain scope where these vulnerable switches operate, reducing the attack surface for adjacent network attackers. Network access control policies should be strengthened to prevent unauthorized physical access to network infrastructure, as the attack requires physical adjacency to the vulnerable devices. Additionally, implementing network monitoring solutions that can detect anomalous LLDP packet behavior and unusual switch reload patterns provides early detection capabilities. The vulnerability aligns with ATT&CK technique T1046 for network service scanning and T1068 for exploit for privilege escalation, making it particularly relevant for organizations implementing comprehensive security frameworks. Regular network vulnerability assessments should include specific scanning for LLDP-related vulnerabilities in network infrastructure devices to prevent exploitation of similar implementation flaws.