Cisco Secure Firewall Management Center (FMC) Static Credentials Vulnerability (CVE-2026-20316)

1. Apply Official Security Patches

Refer to the Cisco Security Advisory to identify and upgrade to the fixed software release for your specific FMC deployment.

2. Temporary Mitigation (Network Isolation)

If immediate patching is not feasible, ensure that the FMC management interface is not exposed to the public internet to significantly reduce the attack surface.

# Restrict access to the FMC management port (HTTPS/443) to trusted internal administrative subnets only
access-list RESTRICT_FMC line 1 permit tcp 10.0.0.0 255.0.0.0 host <FMC_IP> eq 443
access-list RESTRICT_FMC line 2 deny tcp any host <FMC_IP> eq 443

3. Log Auditing

Monitor web interface authentication logs for unexpected successful logins from low-privileged system accounts and subsequent anomalous API activities.

This vulnerability (CVE-2026-20316) exists in the web interface of Cisco Secure Firewall Management Center (FMC) due to the presence of static, hardcoded user credentials for a low-privileged account (CWE-259).

An unauthenticated remote attacker can exploit this vulnerability by logging into the affected system using these static credentials to access sensitive system data. Although the CVSS base score is rated as 5.3 (Medium), Cisco has elevated the Security Impact Rating (SIR) to High because this vulnerability can be chained with other Cisco Secure FMC vulnerabilities to achieve full privilege escalation. This vulnerability is actively exploited in the wild and is listed in the CISA KEV catalog.