CVE-2026-20008 in Secure Firewall Adaptive Security Appliance Software
Summary
by MITRE • 03/04/2026
A vulnerability in a small subset of CLI commands that are used on Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an authenticated, local attacker to craft Lua code that could be used on the underlying operating system as root.
This vulnerability exists because user-provided input is not properly sanitized. An attacker could exploit this vulnerability by crafting valid Lua code and submitting it as a malicious parameter for a CLI command. A successful exploit could allow the attacker to inject Lua code, which could lead to arbitrary code execution as the root user. To exploit this vulnerability, an attacker must have valid Administrator credentials.
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Analysis
by VulDB Data Team • 03/05/2026
This vulnerability resides within the command line interface of Cisco's security appliances, specifically affecting the Adaptive Security Appliance software and Threat Defense software implementations. The flaw manifests in a subset of CLI commands that process user input without adequate sanitization mechanisms, creating a path for privilege escalation through code injection techniques. The vulnerability represents a critical security weakness that directly impacts the integrity and confidentiality of network security infrastructure, as it allows local authenticated attackers to bypass normal access controls and execute arbitrary code with the highest system privileges.
The technical exploitation mechanism leverages improper input validation within the Lua scripting environment that runs beneath the Cisco ASA and FTD operating systems. When administrators submit CLI commands containing malicious Lua code as parameters, the system fails to properly sanitize this input before processing. This lack of input sanitization creates a direct code injection vector where attacker-controlled Lua scripts can be executed with root-level privileges. The vulnerability's impact is amplified by the fact that it requires only valid administrator credentials, which are typically more accessible than system-level credentials, making it particularly dangerous in environments where administrative access is widely distributed.
The operational consequences of this vulnerability extend beyond simple privilege escalation to encompass complete system compromise and potential lateral movement within network environments. An attacker who successfully exploits this vulnerability gains root access to the underlying operating system, enabling them to modify system files, install persistent backdoors, exfiltrate sensitive data, or disrupt network security services. This type of vulnerability directly violates the principle of least privilege and undermines the security model that organizations rely upon for protecting their network infrastructure. The vulnerability's presence in the CLI interface also means that traditional security monitoring tools may not detect the malicious activity, as it operates within the legitimate administrative channels.
Mitigation strategies must address both immediate protective measures and long-term architectural improvements to prevent similar vulnerabilities. Organizations should implement strict input validation controls at all levels of the application stack, particularly focusing on the Lua processing components that handle CLI command parameters. Network segmentation and privilege separation techniques should be enhanced to limit the impact of potential compromises, while comprehensive monitoring of CLI activities should be deployed to detect anomalous command patterns. This vulnerability aligns with CWE-74 and CWE-79 categories related to injection flaws and improper input validation, and maps to ATT&CK techniques involving privilege escalation and command and control operations. Regular security updates and patches should be applied immediately upon availability, while administrative access should be tightly controlled through multi-factor authentication and least privilege principles to minimize the attack surface for such exploits.