CVE-2021-34792 in ASA
Summary
by MITRE • 10/27/2021
A vulnerability in the memory management of Cisco Adaptive Security Appliance (ASA) Software and Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper resource management when connection rates are high. An attacker could exploit this vulnerability by opening a significant number of connections on an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.
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Analysis
by VulDB Data Team • 07/28/2023
The vulnerability identified as CVE-2021-34792 represents a critical memory management flaw in Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) software implementations. This weakness specifically manifests when devices encounter high connection rates, creating a scenario where improper resource handling leads to system instability. The vulnerability affects Cisco's core security infrastructure products that serve as network firewalls and threat defense systems, making it particularly concerning for enterprise security deployments.
From a technical perspective, the flaw stems from inadequate memory allocation and deallocation mechanisms within the connection handling subsystem of these security appliances. When an attacker establishes a large number of concurrent connections, the system's resource management functions fail to properly handle the memory overhead, leading to memory exhaustion or corruption. This improper resource management pattern creates a condition where the device's memory pools become depleted or corrupted, ultimately forcing the system to crash and reload automatically. The vulnerability operates at the software level within the kernel or system services responsible for connection tracking and state management.
The operational impact of this vulnerability extends beyond simple service disruption, as it can affect critical network security operations. Organizations relying on Cisco ASA and FTD appliances for network segmentation, firewall protection, and threat detection face potential security gaps when these devices experience DoS conditions. The automatic reload process creates temporary network outages that can compromise network availability and potentially expose systems to additional threats during the recovery period. This vulnerability particularly affects environments with high network traffic volumes or those under attack from threat actors seeking to exploit security infrastructure weaknesses.
Security professionals should consider this vulnerability in the context of broader attack patterns targeting network infrastructure components. The weakness aligns with common attack techniques described in the MITRE ATT&CK framework under the "Network Denial of Service" and "Resource Hijacking" tactics. Organizations implementing Cisco security appliances should prioritize patch management and monitoring for unusual connection patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper resource management in security appliances and highlights the need for robust testing of high-load scenarios in security device configurations. Mitigation strategies should include implementing connection rate limiting, monitoring for abnormal connection spikes, and applying vendor-provided security updates as soon as they become available.