CVE-2026-20131 Cisco Secure Firewall Management Center (FMC): unsafe data loading
In plain words: The program unpacks saved data from outside without checking it is safe. Usually lets an attacker run code on the server.
Confirmed exploited by CISA on · US federal patch deadline Mar 22, 2026
What to do
- Install Cisco's security update for Secure Firewall Management Center (FMC). If no update exists, follow the vendor's workaround or stop using the product until one ships.
- Patch edge devices first — attackers often start scanning for them within hours of a fix.
- Never expose the device's admin page to the internet.
- After patching a device that was exposed, follow the vendor's compromise checks, end active sessions and change passwords.
Who is affected
Work IT. Aimed mostly at company systems — you are affected through the companies you use, not your own phone.
What's at risk: They face the internet and guard the whole network, so a flaw here can hand attackers a way in — and these devices usually run no antivirus, so break-ins go unnoticed.
The details
- Official name
- Cisco Secure Firewall Management Center (FMC) Software and Cisco Security Cloud Control (SCC) Firewall Management Deserialization of Untrusted Data Vulnerability
- Product
- Cisco Secure Firewall Management Center (FMC)
- CISA description
- 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.
- Type of flaw
- Unsafe data loading (CWE-502)
- Confirmed exploited
- Mar 19, 2026 — known to be used in ransomware attacks
- US federal patch deadline
- Mar 22, 2026
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Answering about CVE-2026-20131 ·
Questions about CVE-2026-20131
Is CVE-2026-20131 being exploited?
Yes. CISA added CVE-2026-20131 to its Known Exploited Vulnerabilities catalog on Mar 19, 2026, which means there is reliable evidence of real-world attacks, including by ransomware groups.
How do I fix CVE-2026-20131?
Install Cisco's security update for Secure Firewall Management Center (FMC). If no update exists, follow the vendor's workaround or stop using the product until one ships. Patch edge devices first — attackers often start scanning for them within hours of a fix.
Am I affected by CVE-2026-20131?
Only if you use Cisco Secure Firewall Management Center (FMC). Aimed mostly at company systems — you are affected through the companies you use, not your own phone.