CVE-2001-0711 in IOS
Summary
by MITRE
Cisco IOS 11.x and 12.0 with ATM support allows attackers to cause a denial of service via the undocumented Interim Local Management Interface (ILMI) SNMP community string.
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Analysis
by VulDB Data Team • 09/02/2024
The vulnerability identified as CVE-2001-0711 represents a significant security flaw in Cisco IOS versions 11.x and 12.0 that incorporate ATM (Asynchronous Transfer Mode) support. This issue specifically targets the Interim Local Management Interface (ILMI) which operates as an undocumented SNMP community string mechanism within Cisco routers. The flaw enables unauthorized actors to exploit a weak authentication mechanism that was never properly documented or secured, creating a potential pathway for malicious users to disrupt network operations. The vulnerability stems from the improper implementation of access controls within the ILMI protocol, which is designed to manage ATM connections and provide local management capabilities for ATM interfaces.
The technical implementation of this vulnerability exploits the lack of proper authentication validation within the ILMI subsystem. When an attacker sends specific SNMP requests using the undocumented community string, the system fails to properly validate the incoming requests and may respond in ways that cause the router to become unresponsive or crash. This occurs because the ILMI interface was designed with minimal security controls and relies on the assumption that only authorized personnel would know the undocumented community string. The vulnerability essentially allows an attacker to send malformed or excessive ILMI requests that can cause the router's memory management or processing functions to fail, resulting in system instability. According to CWE classification, this represents a weakness in the authentication mechanism and falls under CWE-287 for improper authentication, while also demonstrating characteristics of CWE-400 for uncontrolled resource consumption.
The operational impact of this vulnerability extends beyond simple denial of service as it can severely compromise network availability and reliability. When exploited, the vulnerability can cause routers to become completely unresponsive, requiring manual intervention to restore functionality through rebooting or configuration resets. Network administrators may experience extended downtime as the affected routers cannot properly handle ATM traffic or maintain their routing functions. The attack vector is particularly concerning because it does not require sophisticated knowledge or specialized tools, as the undocumented community string may be discovered through simple reconnaissance or by referencing older documentation. This vulnerability affects the fundamental network infrastructure, potentially disrupting communications across large enterprise networks that rely on ATM connections for critical traffic. The impact is further exacerbated by the fact that ATM interfaces were commonly used in high-speed backbone networks, making the exploitation of this vulnerability particularly dangerous for mission-critical systems.
Mitigation strategies for CVE-2001-0711 should focus on immediate network hardening and configuration changes. Network administrators should disable ATM interfaces on affected routers when they are not actively required, as this eliminates the attack surface entirely. The recommended approach involves configuring the router to disable ILMI functionality or implementing strict access controls that limit which systems can communicate with the ILMI interface. Additionally, implementing network segmentation and access control lists can prevent unauthorized systems from reaching the vulnerable interfaces. According to ATT&CK framework, this vulnerability aligns with techniques related to privilege escalation and denial of service, specifically targeting the network infrastructure layer. Organizations should also consider implementing monitoring solutions that can detect unusual ILMI traffic patterns or unauthorized access attempts. Regular security assessments and network audits are essential to identify other potential undocumented interfaces or services that may present similar vulnerabilities. The long-term solution involves upgrading to newer IOS versions that properly implement authentication controls and do not rely on undocumented community strings for management functions.