CVE-2026-20131 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.
From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.
Should You Worry?
- CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 19 Mar 2026.
- CISA lists it as known to be used in ransomware campaigns.
- Rated Critical severity (CVSS 10.0, scored by Vendor).
- This product type is often exposed to the internet, which is where attackers scan for it first.
- It has been in the catalogue for 232 days. Systems still unpatched now have almost certainly been scanned for it.
What It Is
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.
Affected Versions
| Product | Versions |
|---|---|
| Cisco Cisco Secure Firewall Management Center (FMC) | 7.0.0 7.0.0.1 7.0.1 7.1.0 6.4.0.13 7.0.1.1 |
From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.
What To Do Now
- 1
Find it
Search your asset inventory and external attack surface for Cisco Secure Firewall Management Center (FMC). Include cloud images, appliances and anything a supplier runs for you.
Attack Surface Management - 2
Fix it
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Vulnerability Management - 3
Hunt for compromise
If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.
Incident Response - 4
Prove it is fixed
Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.
Penetration Testing
The Compliance Clock
General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.
Not Sure If You Are Exposed?
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