CVE-2011-3298 in Firewall Services Module Software
Summary
by MITRE
Cisco Adaptive Security Appliances (ASA) 5500 series devices, and the ASA Services module in Cisco Catalyst 6500 series devices, with software 7.0 before 7.0(8.13), 7.1 and 7.2 before 7.2(5.3), 8.0 before 8.0(5.24), 8.1 before 8.1(2.50), 8.2 before 8.2(5), 8.3 before 8.3(2.18), 8.4 before 8.4(1.10), and 8.5 before 8.5(1.1) and Cisco Firewall Services Module (aka FWSM) 3.1 before 3.1(21), 3.2 before 3.2(22), 4.0 before 4.0(16), and 4.1 before 4.1(7) allow remote attackers to bypass authentication via a crafted TACACS+ reply, aka Bug IDs CSCto40365 and CSCto74274.
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Analysis
by VulDB Data Team • 11/23/2021
The vulnerability described in CVE-2011-3298 represents a critical authentication bypass flaw affecting Cisco Adaptive Security Appliances and Firewall Services Modules across multiple software versions. This issue specifically targets the TACACS+ authentication mechanism, which is fundamental to secure network access control in enterprise environments. The vulnerability allows remote attackers to manipulate authentication responses and gain unauthorized access to network devices without proper credentials, creating a significant security risk for organizations relying on these Cisco security appliances for network perimeter protection.
The technical flaw stems from improper validation of TACACS+ authentication replies within the affected Cisco ASA and FWSM software versions. When a TACACS+ server responds to an authentication request, the Cisco device should rigorously validate the response to ensure it originates from a legitimate authentication server and contains valid authentication data. However, the vulnerability enables attackers to craft malicious TACACS+ responses that appear legitimate to the device, allowing unauthorized users to bypass the authentication process entirely. This weakness operates at the protocol level where the device fails to properly verify the integrity and authenticity of TACACS+ communications, creating a pathway for unauthorized access. The vulnerability is classified as a weakness in authentication mechanisms, aligning with CWE-287 which addresses improper authentication vulnerabilities, and represents a significant deviation from the expected security controls in network access management systems.
The operational impact of this vulnerability is severe and far-reaching for organizations using affected Cisco devices. Attackers exploiting this vulnerability can gain full administrative access to network security appliances, potentially leading to complete network compromise, data exfiltration, and unauthorized network access. The remote nature of the attack means that adversaries do not require physical access or local network presence to exploit the vulnerability, making it particularly dangerous for perimeter security devices. Organizations may experience unauthorized access to critical network infrastructure, disruption of network services, and potential compliance violations. The vulnerability affects multiple generations of Cisco security appliances, including both standalone ASA devices and modular FWSM implementations, indicating a widespread impact across enterprise network security architectures.
Mitigation strategies for this vulnerability involve immediate software updates and patches provided by Cisco to address the authentication bypass flaw. Organizations should prioritize upgrading their affected ASA and FWSM devices to the latest software versions that contain fixes for Bug IDs CSCto40365 and CSCto74274. Additionally, network administrators should implement network segmentation and access controls to limit the potential impact of exploitation, while monitoring authentication logs for suspicious activity. The ATT&CK framework categorizes this vulnerability under privilege escalation and credential access techniques, making it a critical concern for security operations teams. Organizations should also consider implementing additional authentication layers and monitoring solutions to detect anomalous authentication patterns that may indicate exploitation attempts. The vulnerability highlights the importance of maintaining current security patches and proper protocol validation in network infrastructure devices, particularly those handling critical authentication functions.