CVE-2018-0252 in Wireless LAN Controller Software
Summary
by MITRE
A vulnerability in the IP Version 4 (IPv4) fragment reassembly function of Cisco 3500, 5500, and 8500 Series Wireless LAN Controller Software could allow an unauthenticated, remote attacker to cause an affected device to reload unexpectedly, resulting in a denial of service (DoS) condition. The vulnerability is due to a corruption of an internal data structure process that occurs when the affected software reassembles certain IPv4 packets. An attacker could exploit this vulnerability by sending certain malformed IPv4 fragments to an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition. This vulnerability affects all releases of 8.4 until the first fixed release for the 5500 and 8500 Series Wireless LAN Controllers and releases 8.5.103.0 and 8.5.105.0 for the 3500, 5500, and 8500 Series Wireless LAN Controllers. Cisco Bug IDs: CSCvf89222.
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Analysis
by VulDB Data Team • 03/08/2023
The vulnerability described in CVE-2018-0252 represents a critical denial of service weakness within Cisco's wireless LAN controller software ecosystem. This flaw specifically targets the IPv4 fragment reassembly functionality implemented in Cisco 3500, 5500, and 8500 Series Wireless LAN Controller Software versions. The vulnerability stems from improper handling of malformed IPv4 fragments during the packet reassembly process, creating a condition where the internal data structures become corrupted. This corruption directly impacts the system's ability to maintain stable operation, ultimately leading to unexpected device reloads that disrupt network services. The attack vector requires only an unauthenticated remote connection, making it particularly dangerous as it can be exploited from outside the network perimeter without requiring any credentials or privileged access.
The technical exploitation of this vulnerability occurs through the manipulation of IPv4 packet fragments that are processed during the reassembly phase of network communication. When the affected software encounters specific malformed IPv4 fragments, the internal data structure handling mechanism becomes corrupted, triggering a cascade of errors that ultimately forces the device to undergo an unexpected system reload. This process aligns with CWE-129, which describes improper validation of input ranges, and represents a classic example of how malformed input can lead to system instability. The vulnerability demonstrates a weakness in the software's robustness and error handling capabilities, particularly in the context of network protocol processing where malformed packets are common in various attack scenarios.
The operational impact of this vulnerability extends beyond simple service disruption, as it can affect critical network infrastructure components that support wireless connectivity for enterprise environments. When a wireless LAN controller experiences an unexpected reload, it can cause complete loss of wireless network connectivity for all connected devices, potentially affecting business operations, security monitoring capabilities, and user productivity. The DoS condition created by this vulnerability can be persistent if not addressed promptly, as the device will continue to reload until the attack ceases or the system is manually reset. This vulnerability particularly affects organizations that rely heavily on wireless infrastructure for their network operations, making it a significant concern for enterprise security teams and network administrators who must maintain continuous availability of wireless services.
Organizations affected by this vulnerability should immediately implement mitigation strategies focusing on network segmentation and access control measures. The recommended approach involves deploying network access control lists that filter or block specific types of IPv4 fragments that could trigger the vulnerability, as well as implementing monitoring solutions that can detect unusual reload patterns or traffic patterns associated with exploitation attempts. Network administrators should also consider implementing rate limiting mechanisms to prevent rapid successive fragment transmission that could overwhelm the vulnerable reassembly process. According to ATT&CK framework category T1499, this vulnerability represents a network denial of service attack that could be part of broader reconnaissance or disruption campaigns. The fix for this vulnerability requires upgrading to specific software releases that contain patches addressing the internal data structure corruption issue, with Cisco releasing versions 8.5.103.0 and 8.5.105.0 for the affected series along with appropriate fixes for the 5500 and 8500 Series controllers.