CVE-2020-3554 in ASA
Summary
by MITRE • 10/22/2020
A vulnerability in the TCP packet processing of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to a memory exhaustion condition. An attacker could exploit this vulnerability by sending a high rate of crafted TCP traffic through an affected device. A successful exploit could allow the attacker to exhaust device resources, resulting in a DoS condition for traffic transiting the affected device.
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Analysis
by VulDB Data Team • 11/26/2020
The vulnerability identified as CVE-2020-3554 represents a critical denial of service weakness in Cisco's security infrastructure software, specifically affecting Cisco Adaptive Security Appliance (ASA) and Cisco Firepower Threat Defense (FTD) platforms. This flaw resides within the TCP packet processing mechanisms of these network security devices, creating a pathway for remote attackers to disrupt network operations without requiring authentication credentials. The vulnerability stems from insufficient input validation and resource management within the TCP handling code, which fails to properly account for memory allocation during high-volume packet processing scenarios. Security professionals must recognize this issue as particularly dangerous because it targets fundamental network processing capabilities that are essential for maintaining network connectivity and security posture.
The technical exploitation of CVE-2020-3554 occurs through a memory exhaustion attack vector where malicious actors flood affected devices with specially crafted TCP traffic at high rates. This crafted traffic triggers a condition where the ASA or FTD software continuously allocates memory resources without proper cleanup or bounds checking, leading to progressive memory depletion. The flaw manifests as a failure in the TCP connection state management and packet reassembly processes, where the software's memory pools become exhausted through repeated processing of malformed TCP segments. This type of vulnerability aligns with CWE-129, which addresses improper validation of length of input data, and CWE-131, which covers incorrect calculation of memory buffer size. The attack requires minimal privileges and can be executed from outside the network perimeter, making it particularly dangerous for network security appliances that are designed to protect against such threats.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise entire network infrastructures that depend on these security appliances for traffic control and security enforcement. When exploited successfully, the memory exhaustion condition can cause the affected device to become unresponsive, leading to complete denial of service for all network traffic passing through the appliance. Network administrators may experience extended downtime as the device requires manual intervention to recover from the memory exhaustion state, potentially requiring device restarts or configuration resets. This vulnerability directly impacts the availability aspect of the CIA triad and can be classified under ATT&CK technique T1499.004, which covers network disruption through resource exhaustion attacks. Organizations relying on these security appliances for their network defense may face cascading effects where the DoS condition affects downstream systems and services that depend on uninterrupted network connectivity.
Mitigation strategies for CVE-2020-3554 require immediate implementation of network access controls and traffic filtering measures to prevent exploitation attempts. Organizations should deploy ingress and egress filtering rules to limit TCP traffic rates and implement rate limiting on TCP connections to prevent memory exhaustion attacks. Cisco recommends applying the latest software patches and updates to address the vulnerability, as these releases contain fixes for the memory management issues in TCP packet processing. Network administrators should also implement monitoring solutions to detect unusual traffic patterns that may indicate exploitation attempts, including monitoring for sudden increases in TCP connection establishment rates or memory usage spikes. The implementation of intrusion prevention systems with signatures specifically targeting this vulnerability can provide additional protection layers, while regular security assessments should verify that the mitigation measures are effective against evolving attack techniques targeting similar memory exhaustion vulnerabilities in network security infrastructure.