CVE-2026-20222 in Secure Firewall Adaptive Security Appliance
Summary
by MITRE • 09/16/2026
A vulnerability in the EIGRP implementation in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, adjacent attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition.
This vulnerability is due to improper resource management when handling EIGRP update messages. An attacker could exploit this vulnerability by sending crafted EIGRP updates at a high rate to an affected device. A successful exploit could allow the attacker to trigger a memory leak that will eventually cause the affected device to reload unexpectedly.
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Analysis
by VulDB Data Team • 09/16/2026
The Cisco Secure Firewall Adaptive Security Appliance and Threat Defense software contain a critical implementation flaw within their Enhanced Interior Gateway Routing Protocol processing logic, specifically identified as CVE-2024-20358. This vulnerability stems from improper resource management when the device processes EIGRP update messages. The core technical deficiency lies in how memory is allocated and released during the parsing of these routing protocol packets. When an attacker sends crafted EIGRP updates at a high rate, the system fails to properly free associated data structures or buffers after processing each message. This oversight results in a progressive accumulation of unreleased memory allocations within the device's operating environment. Over time, this continuous allocation without corresponding deallocation leads to a significant memory leak that consumes available system resources until they are exhausted.
The operational impact of this vulnerability is severe, primarily manifesting as a denial of service condition through an unexpected device reload. As the memory leak progresses and depletes the firewall's available RAM, the operating system becomes unstable and unable to maintain normal operations. To prevent total system hang or data corruption, the software triggers an automatic reboot mechanism. This results in a complete interruption of network services managed by the ASA or FTD appliance. For organizations relying on these devices for perimeter security, traffic filtering, and routing decisions, such unexpected reboots can lead to significant downtime, potential loss of session state information, and temporary exposure of internal networks as firewall rules are not enforced during the boot process. The attack requires no authentication but does require network adjacency, meaning an attacker must be able to send packets directly to the affected interface on the same broadcast domain or routed segment.
From a threat intelligence perspective, this vulnerability aligns with CWE-401, which describes missing release of memory after effective usage, and is categorized under MITRE ATT&CK technique T1498, specifically Network Denial of Service via resource exhaustion. The attack vector involves the abuse of legitimate routing protocol functionality to destabilize the host system rather than executing arbitrary code or gaining unauthorized access to data. This distinction highlights that while the immediate goal is disruption, the underlying mechanism relies on exploiting a fundamental software engineering error in memory handling routines within the EIGRP module.
Mitigation strategies for this vulnerability involve applying the latest security patches provided by Cisco as soon as they are available for the specific versions of ASA and FTD software affected. Until patching can be implemented, network administrators should consider implementing access control lists to restrict EIGRP traffic from untrusted sources or adjacent networks that do not require routing protocol adjacency with the firewall interfaces. Additionally, enabling rate limiting on incoming EIGRP updates can help mitigate the speed at which memory is consumed during an attack attempt. Regular monitoring of system resource utilization and logs for signs of high CPU or memory usage spikes may also provide early warning indicators of exploitation attempts in environments where immediate patching is not feasible due to operational constraints.