Exploited vulnerabilities / CVE-2026-20131
Confirmed exploited · insecure deserialization · Cisco Secure Firewall Management Center (FMC)CVE-2026-20131
Cisco Secure Firewall Management Center (FMC) insecure deserialization, confirmed exploited in the wild.
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.
| CISA's name for it | Cisco Secure Firewall Management Center (FMC) Software and Cisco Security Cloud Control (SCC) Firewall Management Deserialization of Untrusted Data Vulnerability |
|---|---|
| Vendor and product | Cisco · Secure Firewall Management Center (FMC) |
| Type | insecure deserialization · CWE-502 |
| Exploited | Confirmed by CISA listed 19 March 2026 |
| Likelihood | one of the most likely to be exploited of every vulnerability tracked |
| Deadline | 22 March 2026 · already passed |
| Used in ransomware | Yes: CISA reports it used in ransomware campaigns |
| Advisories | sec.cloudapps.cisco.com ↗ · nvd.nist.gov ↗ |
Three steps, in this order
Apply the vendor's fix or mitigation; CISA lists only vulnerabilities seen exploited.
If you cannot patch now, restrict network access to the affected product.
Check for signs of compromise since the date it was added to the list.
| CISA's 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. |
|---|
Know before someone else finds it
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CVE-2026-20131 in short
Is CVE-2026-20131 being exploited?
Yes. CISA added CVE-2026-20131 to its Known Exploited Vulnerabilities catalogue on 19 March 2026, which it does only on evidence of exploitation in the wild.
What is the CISA deadline for CVE-2026-20131?
US federal agencies must remediate it by 22 March 2026. Everyone else should treat that date as the latest safe point to patch an internet-facing system.
How likely is CVE-2026-20131 to be exploited in the next 30 days?
FIRST's Exploit Prediction Scoring System gives it 44%, the 98th percentile of every CVE it scores.
How do I fix CVE-2026-20131?
Apply the vendor's fix or mitigation; CISA lists only vulnerabilities seen exploited. If you cannot patch now, restrict network access to the affected product. Check for signs of compromise since the date it was added to the list.
Other Cisco vulnerabilities being exploited
| CVE | Product | Type | Listed |
|---|---|---|---|
| CVE-2026-20320 | BroadWorks | exploited vulnerability | 10 November 2026 |
| CVE-2026-76418 | Secure Firewall ASA Software and Cisco Secure FTD Software | denial of service | 29 October 2026 |
| CVE-2026-76519 | Secure Email Gateway | path traversal | 14 October 2026 |
| CVE-2026-76504 | Catalyst SD-WAN Manager | privilege escalation | 30 September 2026 |
| CVE-2026-76460 | Identity Services Engine | privilege escalation | 16 September 2026 |
| CVE-2026-76461 | Secure Email Gateway | SQL injection | 14 September 2026 |
Sources: CISA Known Exploited Vulnerabilities catalogue (released 10 November 2026) and FIRST EPSS. Page compiled automatically by SAK T.L.M, the threat-intelligence tool of SAK T.E.C, on 13 November 2026.