Cisco Releases Hotfixes for Actively Exploited CVE-2026-20316 Zero-Day in Secure FMC Allowing Static Credential Access

A zero-day vulnerability tracked as CVE-2026-20316 is being actively exploited in Cisco Secure Firewall Management Center, enabling remote attackers to authenticate using hardcoded low-privilege credentials without prior authentication.

The flaw affects a critical component used in many corporate networks and carries a CVSS score of 5.3, yet Cisco has raised its internal severity rating to High because the initial access can be chained with additional vulnerabilities to expand privileges or reach elevated code execution.

Cisco has already distributed hotfixes for branches 7.0, 7.2, 7.4, 7.6, 7.7 and 10.0 with version-specific packages. Administrators are instructed to check license events in /var/log/messages and treat any appearance of the file /var/tmp/license.tmp as suspicious.

The same indicator is also associated with the related critical authentication bypass CVE-2026-20079, which may allow script execution to obtain root access. In environments exposed to both issues, patching should be performed as a combined remediation effort.

The most effective mitigation remains limiting exposure of the management interface to the internet by applying ACLs, VPN access and dedicated management networks. Organizations should also identify all FMC instances and their patch levels, rotate credentials and certificates after suspected activity, and enable telemetry focused on unusual sudo executions and commands involving license utilities such as paquete_info.pl.

U.S. federal civilian agencies have a remediation deadline of August 1, 2026 tied to the Known Exploited Vulnerabilities catalog.