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CVE-2026-20131

10, critical Known exploited Used in ransomware

Cisco Secure Firewall Management Center (FMC) Software and Cisco Security Cloud Control (SCC) Firewall Management Deserialization of Untrusted Data Vulnerability

NVD (opens in a new tab) CVE.org (opens in a new tab) CISA KEV catalogue (opens in a new tab)
CVSS
10, critical critical CVSS v3.1
EPSS, next 30 days
43% higher than 98.7% of scored CVEs
Exploitation
Confirmed in the wild
Published
4 Mar 20267 months ago

Known exploited

CISA added this to the Known Exploited Vulnerabilities Catalog on 19 Mar 2026 and links it to ransomware activity. US federal agencies had to remediate by 22 Mar 2026, a deadline that has passed.

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.

Description

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.

Details

Vendor
Cisco
Product
Cisco Secure Firewall Management Center (FMC)
Weakness
CWE-502 (opens in a new tab)
Status
Analyzed
Updated
17 Jun 2026
Assigner
psirt@cisco.com

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

References 3

Advisories 2

Other references 1

The kind is read from NVD's tags where present and from the shape of the URL otherwise, so treat it as a hint.

Other Cisco CVEs

Every Cisco CVE we hold

Same vendor in what we hold, not a known link between the flaws.

  • CVE-2026-76519 Cisco Secure Email Gateway Relative Path Traversal Vulnerability KEV EPSS 2% 9.8, critical
  • CVE-2026-76504 Cisco Catalyst SD-WAN Manager Hex Encoding Vulnerability KEV EPSS 2% 9.8, critical
  • CVE-2026-76460 Cisco Identity Services Engine Incorrect Use of Privileged APIs Vulnerability KEV EPSS 14% 10, critical
  • CVE-2026-76461 Cisco Secure Email Gateway SQL Injection Vulnerability KEV EPSS 30% 9.8, critical
  • CVE-2026-20349 Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection Vulnerability KEV EPSS 1% 8.6, high
  • CVE-2026-20316 Cisco Secure Firewall Management Center Use of Hard-coded Password Vulnerability KEV EPSS 35% 5.3, medium
  • CVE-2026-20262 Cisco Catalyst SD-WAN Manager Directory or Path Traversal Vulnerability KEV EPSS 28% 6.5, medium
  • CVE-2026-20245 Cisco Catalyst SD-WAN Manager Improper Encoding or Escaping of Output Vulnerability KEV EPSS 25% 7.8, high

Beyond this page

Is CVE-2026-20131 in your network?

This page tells you how dangerous CVE-2026-20131 is out there. Whether it sits on one of your devices, only a scan of your own network can tell. That is what our systems do, every day, for the companies we protect.

CVE-2026-20131 is in the CISA catalogue of exploited vulnerabilities: attackers are already exploiting it.

  • EXYS7600 OCELOT

    Find it before attackers do

    Ocelot scans your network on a schedule and reports every vulnerability it finds by its CVE identifier, with its CVSS score and how many of your hosts are affected. A finding like CVE-2026-20131 comes with the devices to patch.

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  • EXYS7950 KONDRA

    Detect it if it's exploited

    Until the patch is applied, Kondra monitors your network, events and endpoints in real time. It keeps an inventory of the software installed on every endpoint, and its anomaly detection rules flag what an attacker does once inside.

    Learn more about EXYS7950 KONDRA
Check your exposure

Assembled from the NVD 2.0 API, the CISA Known Exploited Vulnerabilities Catalog and FIRST EPSS. Scores are as of our last collection on 17 Oct 2026, not the live upstream state.