CVE-2001-0895 in IOS
Summary
by MITRE
Multiple Cisco networking products allow remote attackers to cause a denial of service on the local network via a series of ARP packets sent to the router s interface that contains a different MAC address for the router, which eventually causes the router to overwrite the MAC address in its ARP table.
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Analysis
by VulDB Data Team • 12/15/2024
The vulnerability described in CVE-2001-0895 represents a significant flaw in Cisco networking equipment that affects multiple router models across various product lines. This issue stems from improper handling of Address Resolution Protocol packets within the router's ARP table management system. The vulnerability allows remote attackers to exploit the router's ARP processing mechanism through carefully crafted sequences of ARP packets that contain spoofed MAC addresses, ultimately leading to a denial of service condition that disrupts network operations.
The technical root cause of this vulnerability lies in the router's failure to properly validate incoming ARP packets before updating its ARP table entries. When a router receives an ARP packet containing a MAC address that differs from the one already stored for a particular IP address, the system should implement proper validation checks to prevent unauthorized modifications. However, this vulnerability demonstrates a lack of such validation mechanisms, allowing malicious actors to repeatedly send ARP packets with conflicting MAC addresses. The router's ARP table becomes progressively corrupted as it continuously overwrites legitimate entries with spoofed values, eventually leading to complete disruption of network communication.
From an operational perspective, this vulnerability poses a serious threat to network availability and stability. The denial of service condition affects the local network segment connected to the vulnerable router, potentially disrupting critical business operations and communications. Network administrators may experience intermittent connectivity issues, complete network outages, or significant performance degradation as the router's ARP table becomes saturated with invalid entries. The attack can be executed remotely without requiring authentication, making it particularly dangerous as it can be exploited by anyone with access to the network segment where the vulnerable router operates.
This vulnerability aligns with CWE-225, which addresses improper validation of input data within network protocols, and demonstrates characteristics consistent with the ATT&CK technique T1498, specifically "Network Denial of Service" where adversaries exploit weaknesses in network infrastructure to disrupt services. The vulnerability also reflects the broader category of protocol-based attacks that target fundamental network functions, similar to techniques described in ATT&CK's T1071 for application layer protocols and T1566 for credential harvesting through network attacks.
Effective mitigation strategies for this vulnerability include implementing ARP inspection mechanisms, enabling dynamic ARP inspection on network switches, and deploying proper access control lists to filter malicious ARP traffic. Cisco released patches and updates to address this issue, which should be applied immediately to all affected router models. Network administrators should also consider implementing ARP monitoring tools to detect anomalous ARP activity patterns and establish regular security audits of network infrastructure to identify potential vulnerabilities. Additional protective measures include segmenting network traffic, implementing proper network access controls, and maintaining up-to-date network security monitoring systems to detect and respond to similar attacks that exploit protocol implementation flaws in network devices.