CVE-2024-20384 in ASA
Summary
by MITRE • 10/23/2024
A vulnerability in the Network Service Group (NSG) feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to bypass a configured access control list (ACL) and allow traffic that should be denied to flow through an affected device.
This vulnerability is due to a logic error that occurs when NSG ACLs are populated on an affected device. An attacker could exploit this vulnerability by establishing a connection to the affected device. A successful exploit could allow the attacker to bypass configured ACL rules.
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Analysis
by VulDB Data Team • 08/01/2025
The vulnerability identified as CVE-2024-20384 resides within the Network Service Group functionality of Cisco Adaptive Security Appliance software and Cisco Firepower Threat Defense software, representing a critical flaw in network security enforcement mechanisms. This issue manifests as a logic error within the NSG Access Control List processing module, where the system fails to properly validate and enforce configured security policies. The vulnerability operates at the core of network traffic filtering operations, directly impacting the device's ability to maintain proper access control boundaries and potentially allowing unauthorized network access.
The technical implementation of this flaw involves a specific logic error that occurs when Network Service Group Access Control Lists are populated and processed on affected Cisco devices. When an attacker establishes a connection to the vulnerable system, the malformed logic within the NSG ACL handling routine fails to properly evaluate and enforce the configured security policies. This creates a pathway where traffic that should be explicitly denied by the configured ACL rules can unexpectedly flow through the device, effectively bypassing the intended security controls. The vulnerability does not require authentication credentials for exploitation, making it particularly dangerous as it can be leveraged by any remote attacker without prior access privileges.
The operational impact of this vulnerability extends far beyond simple network connectivity issues, as it fundamentally undermines the security posture of affected organizations. Network administrators who rely on Cisco ASA and FTD devices for perimeter protection and internal network segmentation face a significant risk of unauthorized access to sensitive systems and data. The bypass of configured ACL rules can lead to lateral movement within networks, potentially allowing attackers to reach critical infrastructure components that should be protected by firewall rules. This vulnerability directly impacts the CIA triad by compromising confidentiality through unauthorized data access and integrity through potential malicious modifications to network traffic flows.
Organizations should implement immediate mitigations including applying the latest security patches provided by Cisco, which address the underlying logic error in the NSG ACL processing functionality. Network segmentation strategies should be enhanced to minimize the impact of potential exploitation, while additional monitoring should be implemented to detect anomalous traffic patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-284 Access Control Bypass and maps to ATT&CK technique T1071.001 Application Layer Protocol DNS, as attackers may leverage this bypass to establish covert communication channels. Security teams should also consider implementing network behavior analysis tools to detect unusual traffic flows that could indicate the exploitation of this vulnerability, while conducting thorough network audits to identify any potential unauthorized access that may have already occurred.