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CISA Flags Cisco Firewall Zero-Day Exploited by Interlock, Sets March 22 Patch Deadline

Amazon researchers say Interlock began abusing CVE-2026-20131 on January 26 as a zero-day.

Overview

  • The flaw in Cisco Secure Firewall Management Center and Security Cloud Control allows unauthenticated remote code execution as root via insecure Java deserialization, earning a CVSS 10.0 rating.
  • Cisco released fixes on March 4 and updated its advisory to confirm in-the-wild exploitation, urging customers to upgrade immediately.
  • Amazon’s MadPot honeypots logged exploit traffic and revealed a misconfigured Interlock server that exposed the group’s toolkit and indicators of compromise now available to defenders.
  • Exposed tools include PowerShell reconnaissance scripts, custom JavaScript and Java remote-access trojans, a memory-resident web shell, HAProxy-based proxying with aggressive log wiping, and ConnectWise ScreenConnect for persistence.
  • CISA added the bug to its Known Exploited Vulnerabilities catalog with a March 22 remediation deadline for federal agencies, and Cisco advises keeping the FMC management interface off the public internet to reduce risk.