CVE-2026-20340: Cisco Secure Firewall Management Center Software Deserialization Arbitrary Root Command Execution Vulnerability
A vulnerability in Cisco Secure FMC Software could allow an authenticated, remote attacker to execute arbitrary commands at the root privilege level. This vulnerability is due to unsecured deserialization of web-management user-controlled data. An attacker could exploit this vulnerability by authenticating to the device and sending a crafted HTTP payload. A successful exploit could allow the attacker to save the crafted payload and then execute it on the underlying operating system as root. To exploit this vulnerability, the attacker must have valid credentials for a user account with at least the role of Security Analyst (read-only).
Affected Software
Event History
Frequently Asked Questions
What level of access does an attacker need to exploit this issue?
The attacker must be able to authenticate remotely with valid credentials for an account assigned at least the Security Analyst (read-only) role. No higher-privileged management role is required.
Can a successful attacker gain privileges beyond those of the compromised account?
Yes. Although exploitation requires a Security Analyst or higher account, successful exploitation can execute arbitrary commands on the underlying operating system with root privileges.
What exploitation path should defenders monitor for?
The described attack uses a crafted HTTP payload sent through the web-management interface after authentication. The payload can be saved and subsequently executed on the underlying operating system as root.