---
title: "CVE-2026-20131: Cisco Secure Firewall Management Center (FMC) Software and Cisco Security Cloud Control (SCC) Firewall Management Deserialization of Untrusted Data Vulnerability"
url: https://erroneo.us/security/cve/CVE-2026-20131/
description: "CVE-2026-20131 (Cisco Secure Firewall Management Center (FMC)): Exploited in the wild (CISA KEV). A vulnerability in the web-based management interface of…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-03-04
date_modified: 2026-08-14
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-20131"
kev: true
cvss: 10
epss: 0.43166
license: All rights reserved. Quote with attribution and a link.
---

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

**Signal:** Exploited: patch now if you run it. CISA has confirmed exploitation in the wild. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Yes, if you run Cisco Secure Firewall Management Center (FMC). CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-03-19, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-03-22 ; treat that as the outer limit, not the target. CISA also lists it as known to be used in ransomware campaigns .
- EPSS 43.2% , percentile 99: FIRST’s model estimates a 43.2% chance of exploitation activity in the next 30 days, higher than 99% of all scored CVEs (very high). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize 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 products (CVE record)

- 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, 6.4.0.14, 7.1.0.1, 7.0.2, 6.4.0.15, 7.2.0, 7.0.2.1

## Severity

- cisco CVSS 3.1: 10 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H`

## Exploitation

- CISA KEV: added 2026-03-19; federal due date 2026-03-22. Known ransomware use: Known.
- 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 SSVC assessment: exploitation active , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 43.17% probability of exploitation activity in the next 30 days; percentile 99.

## Sources

- [Listed in CISA KEV notes (sec.cloudapps.cisco.com)](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fmc-rce-NKhnULJh)
- [CVE.org record CVE-2026-20131](https://www.cve.org/CVERecord?id=CVE-2026-20131)
- [NVD entry CVE-2026-20131](https://nvd.nist.gov/vuln/detail/CVE-2026-20131)
- [CISA Known Exploited Vulnerabilities catalog entry](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-20131)
- [aws.amazon.com](https://aws.amazon.com/blogs/security/amazon-threat-intelligence-teams-identify-interlock-ransomware-campaign-targeting-enterprise-firewalls/)

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Source page: https://erroneo.us/security/cve/CVE-2026-20131/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt