CVE-2001-0375 in PIX
Summary
by MITRE
Cisco PIX Firewall 515 and 520 with 5.1.4 OS running aaa authentication to a TACACS+ server allows remote attackers to cause a denial of service via a large number of authentication requests.
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Analysis
by VulDB Data Team • 08/25/2024
The vulnerability identified as CVE-2001-0375 represents a critical denial of service flaw affecting Cisco PIX Firewall models 515 and 520 when operating with firmware version 5.1.4 and utilizing TACACS+ authentication mechanisms. This issue stems from insufficient input validation within the authentication processing pipeline, specifically when handling authentication requests directed toward TACACS+ servers. The flaw manifests when the firewall receives an excessive volume of authentication requests, causing the system to become unresponsive and ultimately resulting in a complete denial of service condition that affects network access control and security enforcement capabilities.
The technical root cause of this vulnerability lies in the inadequate handling of authentication request volumes within the PIX firewall's TACACS+ client implementation. When multiple authentication requests are processed in rapid succession, the firewall's authentication subsystem fails to properly manage resource allocation and request queuing, leading to memory exhaustion or process starvation conditions. This behavior aligns with CWE-129, Input Validation, and CWE-400, Uncontrolled Resource Consumption, as the system does not properly validate or limit the rate of authentication requests that can be processed. The vulnerability operates at the network security level where authentication services are critical for maintaining access control policies and preventing unauthorized system access.
The operational impact of this vulnerability extends beyond simple service interruption to compromise the fundamental security posture of networks relying on these firewalls. Organizations utilizing affected PIX models may experience complete loss of network access control functionality, potentially allowing unauthorized users to bypass authentication mechanisms while legitimate users are denied access to network resources. The denial of service condition affects the firewall's ability to perform its primary security functions, including packet filtering, stateful inspection, and authentication enforcement. This vulnerability particularly impacts enterprise networks where the PIX firewall serves as a critical security boundary device, potentially creating a window of opportunity for attackers to exploit other security weaknesses or conduct further reconnaissance activities.
Mitigation strategies for CVE-2001-0375 should prioritize immediate firmware upgrades to versions that address the authentication request handling flaw, specifically targeting the TACACS+ client implementation improvements. Network administrators should implement rate limiting mechanisms at network boundaries to prevent excessive authentication requests from reaching the affected firewalls, while also establishing monitoring protocols to detect unusual authentication traffic patterns. The implementation of redundant authentication servers and load balancing solutions can help distribute authentication requests and reduce the likelihood of triggering the vulnerability. Security teams should also consider implementing intrusion detection systems capable of identifying patterns consistent with this specific denial of service attack vector. According to ATT&CK framework domain T1499, Endpoint Denial of Service, this vulnerability represents a classic example of how authentication service vulnerabilities can be exploited to achieve system-wide denial of service conditions, making it a critical target for both preventive and reactive security measures. Organizations should also conduct regular vulnerability assessments to identify other potential authentication-related weaknesses that could compound the impact of such denial of service conditions.