Cisco Secure Firewall Management Center (FMC) Software and Cisco Security Cloud Control (SCC) Firewall Management Deserialization of Untrusted Data Vulnerability

Cisco Secure Firewall Management Center (FMC) Software and Cisco Security Cloud Control (SCC) Firewall Management contain a deserialization of untrusted data vulnerability in the web-based management interface that could allow an unauthenticated, remote attacker to execute arbitrary Java code as root on an affected device.

Published Mar 4, 2026 · Updated May 16, 2026

Why patchRisk explained in plain English

Worst-case scenarioIf unpatched

A remote attacker, without authentication, can achieve full data confidentiality loss, arbitrary modification of data, complete denial of service or system unavailability. CISA has confirmed use of this vulnerability in known ransomware campaigns — treat as high priority for remediation. Federal agencies are required to remediate by 2026-03-22 under CISA BOD 22-01.

How the attack worksNo clicks needed

This is a Deserialization of Untrusted Data (CWE-502) vulnerability in Cisco Secure Firewall Management Center (FMC). A vulnerability in the web-based management interface of Cisco Secure Firewall Management Center (FMC) Software could allow an unauthenticated, remote attacker to execute arbitrary Java code as root on an affected device. This vulnerability is due to insecure deserialization of a user-supplied Java byte stream. An attacker could exploit this vulnerability by sending a crafted serialized Java object to the web-based management interface of an affected device. A successful exploit could allow the attacker to execute arbitrary code on the device and elevate privileges to root. Note: If the FMC management interface does not have public internet access, the attack surface that is associated with this vulnerability is reduced. Exploitation requires remote network access, low attack complexity, no authentication required, and no user interaction required.

📧

Phishing link

→

🖼

Malicious file

🔓

Server compromised

Am I affected?Quick check

Probably yes if any of these apply:

●Network Security Team

●Firewall Administrators

●IT Security

●Running secure firewall management center: 6.4.0.13, 6.4.0.14, 6.4.0.15, 6.4.0.16, 6.4.0.17, 6.4.0.18, 7.0.0, 7.0.0.1, 7.0.1, 7.0.1.1, 7.0.2, 7.0.2.1, 7.0.3, 7.0.4, 7.0.5, 7.0.6, 7.0.6.1, 7.0.6.2, 7.0.6.3, 7.0.7, 7.0.8, 7.0.8.1, 7.1.0, 7.1.0.1, 7.1.0.2, 7.1.0.3, 7.2.0, 7.2.0.1, 7.2.1, 7.2.2, 7.2.3, 7.2.3.1, 7.2.4, 7.2.4.1, 7.2.5, 7.2.5.1, 7.2.5.2, 7.2.6, 7.2.7, 7.2.8, 7.2.8.1, 7.2.9, 7.2.10, 7.2.10.1, 7.2.10.2, 7.3.0, 7.3.1, 7.3.1.1, 7.3.1.2, 7.4.0, 7.4.1, 7.4.1.1, 7.4.2, 7.4.2.1, 7.4.2.2, 7.4.2.3, 7.4.2.4, 7.4.3, 7.4.4, 7.4.5, 7.6.0, 7.6.1, 7.6.2, 7.6.2.1, 7.6.3, 7.6.4, 7.7.0, 7.7.10, 7.7.10.1, 7.7.11, 10.0.0

Real-world incidentsWhat we've seen

Used in known ransomware campaigns. Threat-research write-up: https://aws.amazon.com/blogs/security/amazon-threat-intelligence-teams-identify-interlock-ransomware-campaign-targeting-enterprise-firewalls/

How to patch

Manual remediation steps

Apply the Vendor Patch

This vulnerability is in the CISA Known Exploited Vulnerabilities catalog — apply the vendor's security update as soon as possible.

CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

References

Vendor advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fmc-rce-NKhnULJh

NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2026-20131

CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-20131

PowerShell automationComing soon

No tested PowerShell script for this entry yet. We’re prioritising automation based on user demand.

References

↗ CVE-2026-20131 ↗ NVD ↗ Vendor Advisory