CVE-2011-1640 in IOS
Summary
by MITRE
The ethernet-lldp component in Cisco IOS 12.2 before 12.2(33)SXJ1 does not properly support a large number of LLDP Management Address (MA) TLVs, which allows remote attackers to cause a denial of service (device crash) via crafted LLDPDUs, aka Bug ID CSCtj22354.
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Analysis
by VulDB Data Team • 11/24/2021
The vulnerability described in CVE-2011-1640 represents a critical denial of service flaw within Cisco IOS networking equipment, specifically affecting the ethernet-lldp component in versions prior to 12.2(33)SXJ1. This issue manifests through improper handling of LLDP Management Address TLVs, which are part of the Link Layer Discovery Protocol implementation that enables network devices to advertise their identity, configuration, and capabilities to neighboring devices. The flaw exploits a buffer management weakness that occurs when the system receives a large number of these specific TLVs in a single LLDPDU packet, causing the device to become unstable and eventually crash.
The technical root cause of this vulnerability lies in the insufficient validation and handling of Management Address TLVs within the LLDP implementation. When a malicious actor crafts specially designed LLDPDUs containing an excessive number of MA TLVs, the ethernet-lldp component fails to properly process these packets, leading to memory corruption and ultimately a device crash. This behavior aligns with CWE-121, which describes heap-based buffer overflow conditions, and represents a classic example of inadequate input validation in network protocol implementations. The vulnerability operates at the network layer and affects the device's ability to maintain stable operation, as demonstrated by the specific error conditions that occur during packet processing.
The operational impact of this vulnerability extends beyond simple device unavailability, as it represents a potential vector for network disruption attacks that could affect critical infrastructure. Network administrators face significant operational challenges when dealing with such vulnerabilities, particularly in environments where network stability is paramount. The vulnerability affects all Cisco IOS devices running affected versions, including routers, switches, and other network infrastructure components that implement LLDP functionality. Attackers can exploit this weakness remotely without requiring authentication, making it particularly dangerous in unsecured network environments where LLDP traffic may traverse untrusted networks.
Mitigation strategies for this vulnerability require immediate patching of affected Cisco IOS versions to the recommended release 12.2(33)SXJ1 or later, which includes proper handling of large numbers of MA TLVs. Network administrators should also implement network segmentation and access control measures to limit exposure, particularly by filtering LLDP traffic at network boundaries. Additionally, monitoring systems should be enhanced to detect unusual LLDP traffic patterns that might indicate exploitation attempts. The remediation approach aligns with ATT&CK technique T1499.001, which involves network denial of service attacks, and requires organizations to maintain updated vulnerability management processes to address such threats effectively. Organizations should also consider implementing network access control lists to restrict LLDP traffic from untrusted sources and establish procedures for regular IOS version updates to prevent similar vulnerabilities from impacting their network infrastructure.