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CVE-2026-20131: Cisco Secure Firewall Management Center (FMC) Software and Cisco Security Cloud Control (SCC) Firewall Management Deserialization of Untrusted Data Vulnerability

In short

Cisco Secure Firewall Management Center (FMC) has a weakness classified as deserialization of untrusted data (CWE-502). CISA added it to its Known Exploited Vulnerabilities catalog on 2026-03-19. NVD lists CVSS 3.1 at 10 CRITICAL. CISA reports known ransomware campaign use.

What it is

“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 KEV, retrieved 2026-11-01
“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.” — NVD, retrieved 2026-11-01

Who is affected

Cisco Secure Firewall Management Center (FMC). NVD lists the following versions as affected:

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

Exploitation status

CISA KEV added: 2026-03-19. Known ransomware campaign use: Known (reported by CISA). Due date CISA set for US federal civilian agencies: 2026-03-22.

Scores

NVD CVSS 3.1: 10 CRITICAL; vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H; source [email protected].

EPSS by FIRST: 44.43%; percentile 98.76; score date 2026-10-31. EPSS estimates the probability of exploitation in the next 30 days.

CWE: CWE-502.

Timeline

Source events
DateEvent
2026-03-04T18:16:27.153NVD published
2026-03-19CISA KEV added
2026-03-22CISA KEV due
2026-06-17T10:17:10.937NVD last modified
2026-10-31FIRST EPSS score

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.” — CISA KEV

What to do

  • Confirm whether you run Cisco Secure Firewall Management Center (FMC) and which version.
  • Apply the vendor update or mitigation in the advisory.
  • Follow CISA’s required action.
  • Review the vendor guidance on signs of compromise.
  • Track the fix through completion.

References

Sources and dates

CISA Known Exploited Vulnerabilities Catalog, version 2026.10.30; retrieved 2026-11-01. CISA KEV data: CC0 1.0. No endorsement by CISA.

NVD retrieved: 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.

EPSS scores by FIRST; score date 2026-10-31.

Check your own domain's public security settings

The snapshot checks a domain you own or are authorized to check for DNS, HTTPS/TLS and web-header hygiene. It does not test for this CVE.

Check your own domain's public security settingsBook a scoping call