Cisco FMC Flaws Exploited to Steal Credentials and Deploy Qilin Ransomware

Cisco has revealed that three distinct threat clusters linked to ransomware and state-sponsored attacks have been exploiting two recently patched Secure Firewall Management Center (FMC) vulnerabilities.

The attacks leverage CVE-2026-20079 (CVSS score: 10.0), an authentication bypass vulnerability in the web interface of FMC software that could allow an unauthenticated, remote attacker to bypass authentication and execute script files on an affected device to obtain root access to the underlying operating system.

The second flaw under exploitation is CVE-2026-20316 (CVSS score: 5.3), which could allow an unauthenticated, remote attacker to log in to an affected device using a low-privilege account to access sensitive data within susceptible systems. It can be paired with other Cisco Secure FMC vulnerabilities to elevate privileges.

Cisco Talos said it identified three clusters of post-compromise activity of FMC instances associated with state-sponsored and crimeware threat actors. These include -

• UAT-12197, which has exploited CVE-2026-20079 to deploy JSP-based web shells and a Java Archive (JAR)-based command executor to query internal databases and obtain user authentication data and credentials
• UAT-11823, which has exploited both CVE-2026-20079 and CVE-2026-20316 to deliver a Netcat-based reverse shell, two bash scripts to harvest managed-device configurations, and a variant of Cyclops Blink, a modular ELF implant previously attributed to the Russian state-sponsored hacking group Sandworm
• UAT-11988, a ransomware operation that has exploited CVE-2026-20316 for initial access and then used legitimate built-in FMC tooling as part of a living-off-the-land (LotL) attack to conduct extensive reconnaissance of the victim's environment, drop tunneling tools to maintain network access, collect credentials, build a target list of endpoints to encrypt, terminate security tools, and deploy Qilin ransomware on selected systems.

"Customers are strongly advised to apply hotfixes for affected software versions already released by Cisco for CVE-2026-20079 and CVE-2026-20316," Cisco said, adding it intends to ship a comprehensive hardening release for various internally discovered vulnerabilities next week.

The development comes as the U.S. Cybersecurity and Infrastructure Security Agency (CISA) added CVE-2026-20079 to its Known Exploited Vulnerabilities (KEV) catalog, requiring Federal Civilian Executive Branch (FCEB) agencies to apply the patches by September 12, 2026. The second vulnerability, CVE-2026-20316, was added to the KEV catalog in late July 2026.