CVE-2001-0041 in CatOS
Summary
by MITRE
Memory leak in Cisco Catalyst 4000, 5000, and 6000 series switches allows remote attackers to cause a denial of service via a series of failed telnet authentication attempts.
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Analysis
by VulDB Data Team • 08/21/2024
The vulnerability identified as CVE-2001-0041 represents a critical memory leak flaw affecting Cisco Catalyst 4000, 5000, and 6000 series network switches. This issue stems from inadequate memory management within the switch's telnet authentication mechanism, creating a persistent resource depletion condition that can be exploited remotely. The flaw specifically manifests during authentication attempts, where failed login sequences fail to properly release allocated memory resources, leading to progressive memory consumption over time. This vulnerability operates under the broader category of memory management errors classified as CWE-401, which encompasses improper handling of memory allocation and deallocation processes. The affected Cisco switches operate with a specific implementation of telnet services that does not adequately implement proper resource cleanup protocols, particularly when handling authentication failures.
The technical exploitation of this vulnerability occurs through repeated unsuccessful telnet authentication attempts, where each failed connection attempt consumes a small amount of memory that is never properly freed. As attackers repeatedly attempt to authenticate using invalid credentials, the switch's memory allocation pools gradually become exhausted, eventually leading to system instability and complete service disruption. The memory leak is particularly insidious because it occurs incrementally, making it difficult to detect during normal network operations while slowly degrading system performance. Network administrators may observe increasing memory usage patterns or system sluggishness before recognizing the onset of a full denial of service condition. This behavior aligns with ATT&CK technique T1499.004, which describes resource exhaustion attacks targeting network infrastructure devices.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise network availability and business continuity. When the memory leak reaches critical levels, the affected switch may become unresponsive to legitimate telnet connections, preventing network administrators from accessing the device for maintenance or troubleshooting. This denial of service condition affects not only remote management capabilities but also impacts the overall network infrastructure reliability, as these switches serve as critical components in enterprise and service provider networks. The vulnerability is particularly concerning in environments where automated monitoring systems rely on telnet connectivity for device management, as the compromised switch may become unreachable during critical network events. The flaw demonstrates poor defensive programming practices and inadequate input validation, creating a condition where external attackers can systematically degrade network infrastructure performance through simple credential guessing attacks.
Mitigation strategies for CVE-2001-0041 involve implementing multiple layers of security controls to protect against unauthorized telnet access and prevent exploitation of the memory leak. Network administrators should disable telnet services entirely and migrate to more secure remote access protocols such as SSH, which provide better authentication handling and memory management. Access control lists should be implemented to restrict telnet access to specific IP addresses, reducing the attack surface available to potential exploiters. Additionally, implementing rate limiting or connection throttling mechanisms can help prevent rapid successive authentication attempts that trigger the memory leak. Regular monitoring of switch memory usage and system logs should be established to detect early signs of memory exhaustion. Cisco released patches and firmware updates addressing this vulnerability, requiring immediate deployment of security updates to protect affected devices. The remediation process should include comprehensive testing of updated firmware to ensure that the memory leak has been properly resolved without introducing new compatibility issues. Organizations should also consider implementing network segmentation and access controls to limit potential attackers' ability to reach vulnerable switch devices, thereby reducing the risk of exploitation through this and similar vulnerabilities.