CRITICAL CVSS 10.0
Published: 2026-03-04

CVE-2026-20131

cisco secure_firewall_management_center Security Advisory (CVE-2026-20131)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-20131 impacting cisco secure_firewall_management_center. Evaluated with CVSS Base Score of 10.0 (CRITICAL).

Original NVD Description

Source: NIST NVD
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.

📊 CVSS v3.1 Metric Breakdown

Attack Vector
Network (AV:N)
Exploitable remotely across internet boundaries
Attack Complexity
Low (AC:L)
No specialized conditions required
Privileges Required
None (PR:N)
Unauthenticated execution
User Interaction
None (UI:N)
Zero human interaction required
Scope
Changed (S:C)
Impacts components beyond caller authority
Confidentiality
High (C:H)
Total information disclosure
Integrity
High (I:H)
Total modification of target system
Availability
High (A:H)
Total denial of service or shutdown

🎯 Affected Versions Matrix

Affected Product cisco / secure_firewall_management_center
Affected Versions 6.4.0.13
Weakness Enumeration CWE-502

Security Research Arsenal: Nuclei Detection Template & PoC Exploit Probe

High-Intent Research Tool

Ready-to-use security scanner signatures, active verification probe skeletons, and remediation playbooks for CVE-2026-20131 impacting cisco secure_firewall_management_center.

⚡ Nuclei Detection Template (YAML) cve-2026-20131.yaml
id: cve-2026-20131

info:
  name: cisco secure_firewall_management_center - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: critical
  description: |
    Automated signature & scanner for CVE-2026-20131 affecting cisco secure_firewall_management_center.
    Evaluation: A vulnerability in the web-based management interface of Cisco Secure Firewall Management Center (FMC) Software could allow an unauthenticated, remote...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-20131
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
    cvss-score: 10.0
    cve-id: CVE-2026-20131
    cwe-id: CWE-502
  tags: cve,cve-2026-20131,cisco,secure_firewall_managemen,critical

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "secure_firewall_management_center"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-20131.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-20131
# Target: cisco secure_firewall_management_center | CVSS: 10.0 (CRITICAL)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-20131 (cisco secure_firewall_management_center)...")
    headers = {
        "User-Agent": "CyberVault-Audit-Scanner/2.0",
        "Accept": "*/*"
    }
    try:
        r = requests.get(f"{target_url.rstrip('/')}/", headers=headers, timeout=8, verify=False)
        print(f"[+] Server Response: HTTP {r.status_code} | Server Banner: {r.headers.get('Server', 'Unknown')}")
        if r.status_code < 500:
            print(f"[!] Target reachable. Verify version against cisco secure_firewall_management_center scope (6.4.0.13).")
        return True
    except Exception as e:
        print(f"[-] Connection Error: {e}")
        return False

if __name__ == '__main__':
    url = sys.argv[1] if len(sys.argv) > 1 else "http://localhost:8080"
    verify_vulnerability(url)
🛡️ Quick Patch & Remediation Script (Bash) patch_cve-2026-20131.sh
# Recommended Remediation & Patching Commands for CVE-2026-20131
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install secure_firewall_managemen 2>/dev/null || \
sudo dnf upgrade secure_firewall_managemen 2>/dev/null || \
sudo yum update secure_firewall_managemen

# 2. Inspect installed package versions for vulnerable scope:
dpkg -l | grep -i secure_firewall_managemen 2>/dev/null || rpm -qa | grep -i secure_firewall_managemen

# 3. Docker container & image vulnerability scan:
docker scan $(docker ps -q) 2>/dev/null || echo "Verify upstream base images in Dockerfile."

🛡️ Remediation & Security Action

  • Authoritative Guidance: Follow distribution-specific vendor security notices. Advisory status and package patches vary by distribution release.
  • Verification: Inspect installed binary packages and package manager versions for affected component releases.
  • Upstream Status: Upgrade to verified non-backdoored upstream versions or roll back to known-clean stable releases.
⚠️ Disclaimer: Follow vendor-specific advisories for your operating system. CyberVault does not fabricate unsupported remediation scripts.

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2026-20131 in cisco secure_firewall_management_center?

Review vendor-specific security notices and update cisco secure_firewall_management_center packages to the latest patched release immediately. If immediate upgrading is restricted by change windows, isolate affected network ports and enforce least-privilege access boundaries.

Is there an active exploit or public PoC for CVE-2026-20131?

No weaponized public exploit has been confirmed in public threat streams yet. Continuous surveillance is active across GitHub and security feeds.

What is the CVSS 3.1 severity rating and impact for CVE-2026-20131?

CVE-2026-20131 is classified with a CVSS 3.1 Base Score of 10.0 (CRITICAL). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
10.0
CRITICAL SEVERITY
CVE ID CVE-2026-20131
Weakness CWE-502
Vendor cisco
Product secure_firewall_management_center
Published 2026-03-04
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H