CVE-2013-5513 in ASA
Summary
by MITRE
Cisco Adaptive Security Appliance (ASA) Software 8.2.x before 8.2(5.46), 8.3.x before 8.3(2.39), 8.4.x before 8.4(7), 8.5.x before 8.5(1.18), 8.6.x before 8.6(1.12), 8.7.x before 8.7(1.7), 9.0.x before 9.0(3.3), and 9.1.x before 9.1(1.8), when the DNS ALPI engine is enabled for TCP, allows remote attackers to cause a denial of service (device reload) via crafted TCP DNS packets, aka Bug ID CSCug03975.
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Analysis
by VulDB Data Team • 05/26/2021
The vulnerability identified as CVE-2013-5513 represents a critical denial of service flaw within Cisco Adaptive Security Appliance software versions spanning multiple release branches. This weakness specifically affects the DNS ALPI engine when operating in TCP mode, creating a pathway for remote attackers to deliberately crash the security appliance and force a complete device reload. The affected versions include ASA software 8.2.x through 9.1.x, with each major release branch having specific patch levels that address this vulnerability. The issue stems from insufficient input validation within the application layer protocol inspection framework that processes DNS traffic, making it particularly dangerous as it can be exploited without authentication or prior access to the network infrastructure.
The technical implementation of this vulnerability involves the manipulation of TCP DNS packets that traverse the ASA device when the DNS ALPI engine is actively enabled. When the appliance processes these crafted packets, the malformed data triggers an unexpected behavior in the DNS inspection module, leading to a memory corruption state that ultimately results in the device crashing and requiring a complete restart. This flaw operates at the application layer, specifically targeting the protocol inspection capabilities that allow the ASA to analyze and filter DNS traffic based on established security policies. The vulnerability demonstrates characteristics consistent with CWE-129 Input Validation and Output Encoding, where insufficient validation of input data leads to system instability and potential service disruption. The attack vector requires only network access to the affected ASA device, making it particularly concerning for network security administrators who must protect against remote exploitation.
The operational impact of this vulnerability extends beyond simple service interruption, as the device reload process can result in significant network downtime and potential security gaps during the recovery period. Organizations relying on ASA appliances for network security may experience complete loss of traffic filtering capabilities during the device restart, creating temporary exposure to network threats. The vulnerability affects the availability aspect of the CIA security triad, potentially enabling attackers to perform sustained denial of service attacks that could disrupt critical business operations or compromise network security posture. Network administrators face the challenge of maintaining security while addressing the vulnerability, as patching requires careful planning and execution to avoid service disruption. This flaw aligns with ATT&CK technique T1499.004 for Network Denial of Service, where adversaries exploit weaknesses in network infrastructure to deny access to services or systems.
Mitigation strategies for CVE-2013-5513 require immediate attention from network security teams, with the most effective approach being the application of vendor-supplied patches to the affected ASA software versions. Organizations should prioritize patching across all affected release branches, ensuring that the specific patch levels mentioned in the advisory are implemented to address the vulnerability. Alternative mitigation approaches include disabling the DNS ALPI engine for TCP traffic when it is not essential for security policy enforcement, or implementing network segmentation to limit access to the affected appliances. Security monitoring should be enhanced to detect unusual traffic patterns that may indicate exploitation attempts, and network administrators should consider implementing intrusion detection systems that can identify malformed DNS packets. The vulnerability serves as a reminder of the importance of maintaining up-to-date security software and the critical need for regular vulnerability assessments to identify and remediate similar weaknesses in network infrastructure components. Organizations should also review their patch management procedures to ensure rapid deployment of security updates while maintaining operational stability across their network security infrastructure.