CVE-2011-2057 in IOS
Summary
by MITRE
The cat6000-dot1x component in Cisco IOS 12.2 before 12.2(33)SXI7 does not properly handle (1) a loop between a dot1x enabled port and an open-authentication dot1x enabled port and (2) a loop between a dot1x enabled port and a non-dot1x port, which allows remote attackers to cause a denial of service (traffic storm) via unspecified vectors that trigger many Spanning Tree Protocol (STP) Bridge Protocol Data Unit (BPDU) frames, aka Bug ID CSCtq36327.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 11/24/2021
The vulnerability identified as CVE-2011-2057 affects the cat6000-dot1x component within Cisco IOS versions 12.2 prior to 12.2(33)SXI7, representing a critical flaw in network authentication and switching operations. This issue specifically targets the handling of authentication loops within the IEEE 802.1X port-based network access control framework, where the system fails to properly manage certain port configuration scenarios that create network loops. The vulnerability manifests in two distinct scenarios: when a dot1x enabled port creates a loop with another dot1x enabled port that has open authentication, and when a dot1x enabled port connects to a non-dot1x port, both of which can trigger catastrophic network behavior.
The technical flaw stems from inadequate loop detection and handling mechanisms within the switching fabric's authentication processing. When these specific port configurations are established, the system enters a state where Spanning Tree Protocol BPDU frames are continuously transmitted and received in an endless loop, creating a traffic storm that rapidly consumes network resources. This condition, classified as a denial of service attack, occurs because the switch cannot properly identify and block the looping traffic patterns that arise from the mismatched authentication states between connected ports. The vulnerability operates at the data link layer, specifically affecting the switching operations that manage port authentication states and the associated STP operations that maintain network topology stability.
The operational impact of this vulnerability is severe and can result in complete network disruption across affected Cisco Catalyst 6000 series switches. Network administrators may experience complete loss of network connectivity as the traffic storm consumes available bandwidth and processing resources, potentially requiring manual intervention to restore normal operations. The vulnerability affects network availability and reliability, as legitimate traffic becomes impossible to forward through the affected switch ports. Additionally, the issue can cause cascading failures throughout the network topology as STP operations become overwhelmed by the excessive BPDU traffic, potentially leading to extended network outages that can span multiple switch layers.
This vulnerability aligns with CWE-399, which covers Resource Management Errors, and specifically relates to improper handling of network loop conditions in switching environments. From an ATT&CK framework perspective, this represents a denial of service attack technique that leverages network protocol misconfigurations to exhaust system resources. The attack vector requires remote network access to establish the problematic port configurations, making it particularly concerning for network administrators who may not immediately detect the conditions that trigger the vulnerability. Organizations should implement immediate mitigation measures including network segmentation, proper port configuration management, and monitoring for unusual STP BPDU traffic patterns to prevent exploitation of this vulnerability.
Cisco addressed this issue through the release of IOS software updates that include enhanced loop detection and handling mechanisms specifically for the dot1x component. The recommended solution involves upgrading to IOS version 12.2(33)SXI7 or later, which includes fixes that properly detect and prevent the conditions that lead to the traffic storm. Network administrators should also implement proper network design practices that avoid creating the specific port configurations that trigger the vulnerability, including ensuring consistent authentication states across connected ports and implementing proper network segmentation strategies. Regular network monitoring for unusual STP BPDU activity and implementing automated detection mechanisms can help identify potential exploitation attempts before they cause significant network disruption.