CVE-2026-20324

Cisco Secure Firewall Management Center sftunnel Root Arbitrary Code Exectution Vulnerability

Public exploit available. Not confirmed exploited in the wild yet. No fix published yet.

CVSS 3.19.9Critical EPSS percentile36th0.4% chance in 30 days CISA KEVNot listedNo confirmed exploitation
Public exploit: 0 sources FixNone yetNo fix or workaround published

Published 2026-09-16Updated 2026-09-18Sources: CVE.org, NVD

NVD CVE.org

What to do

No fixed build or workaround is published yet. Limit exposure and watch for a patch.

Steps

Written by AI from the record

Check whether you run Cisco Secure Firewall Management Center (FMC) and identify its installed software version.
Restrict FMC management access to trusted administrators and networks while you review exposure.
No vendor fixed version or patch information is currently available; ask Cisco or your support provider for the applicable update and deployment timeline.
Review administrator accounts and remove or reset access that is no longer needed.

May need vendor or contractor work

Is your organisation exposed?Request an assessment to establish which checks fit your systems.

What it is

From the CVE record

A vulnerability in the sftunnel inter-device communication protocol of Cisco Secure Firewall Management Center (FMC) Software could allow an authenticated, remote attacker to execute arbitrary commands as root. This vulnerability exists because a registered sftunnel peer has incorrect permissions to write an arbitrary file to any location on the device. An attacker could exploit this vulnerability by hijacking the sftunnel communication connection or being a valid registered sftunnel peer and sending an sftunnel command to write a malicious file to the disk of an affected device. A successful exploit could allow the attacker to write a file to the device that is executed with root privileges. To exploit this vulnerability, the attacker must have valid user credentials on the affected device.

In plain language

Written by AI from the record

Cisco Secure Firewall Management Center (FMC) has a critical flaw that lets a logged-in attacker take full control of the device; affected versions are not yet known.

Authenticated remote root code execution in Cisco Secure Firewall Management Center (FMC) through incorrect file-write permissions in the sftunnel inter-device communication protocol.

If you're affected

Full firewall-management takeover
Network security policy changes
Sensitive network data exposure
Service disruption

What is it

This is a weakness in the system used to manage your network firewall. It is like giving someone with a building access badge the ability to replace the master keys: an attacker who gets valid access could take control of the management system and change what it does.

Who is affected

This matters to you if you run Cisco Secure Firewall Management Center (FMC) to manage firewall devices. An attacker needs valid user credentials on the affected device and must be able to act as, or take over, a registered connection between managed devices.

How urgent is it

A public exploit is available, making this a high-priority risk for organizations running the product. Act now to limit management access, review administrator accounts, and obtain Cisco guidance because no patch information is currently available.

What to do — in detail

Confirm whether Cisco Secure Firewall Management Center (FMC) is deployed, record its exact software version, and identify every system permitted to connect through sftunnel. Review FMC user accounts, registered sftunnel peers, and management-network access for unauthorized or unnecessary entries.

No fixed versions or patches are available in the findings, so there is no supported target version to name yet. If patching is delayed, restrict FMC administrative access to a dedicated trusted management network, limit access to only required administrators and registered peers, and reset or revoke unnecessary credentials.

There is no CISA KEV due date because this CVE is not listed in KEV. Monitor Cisco advisories for a fixed release, and investigate unexpected file changes, newly registered peers, unusual sftunnel activity, and administrator-account changes.

Technical context

CVSS 9.9 (Critical): CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H. The weakness is CWE-862, involving incorrect authorization that allows a registered sftunnel peer to write an arbitrary file; the file can then execute with root privileges. Exploitation requires valid FMC credentials and either hijacking an sftunnel connection or operating as a valid registered peer. A public exploit is available. CISA KEV does not list this CVE. EPSS is 0.4% (38th percentile) with a flat trend.

This is a general assessment based on public vulnerability data. It does not account for your specific infrastructure — when in doubt, consult a security specialist.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS36th

Public exploit

CISA KEV

Not in the catalog. CISA has not confirmed exploitation.

Public exploits

0 sources with a proof of concept or module.

Exploit links, PoCs and Metasploit modules after sign-in

EPSS

0.4% chance of exploitation activity in the next 30 days, which ranks it in the 36th percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Lifecycle

6 events over 2 days, from the signal feeds we watch.

2026-09-18Record updated
2026-09-17Record updated
2026-09-16Publishedweakness classified, att&ck mapped, record updated

Affected products

Ciscocommercial · USaka cisco systems inc., cisco systems
- Cisco Secure Firewall Management Center (FMC)Networking Infrastructure

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

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

Scored 9.9 by NVD.

How it is reached

Attack Vector NetworkExploitable remotely over the network without any special conditions
Attack Complexity LowNo special conditions — the attack can be reliably reproduced
Privileges Required LowRequires basic user-level privileges
User Interaction NoneNo user interaction needed — fully automated exploitation

Scope

Scope ChangedThe exploit can affect other components (e.g. sandbox escape, host compromise from VM)

Impact if exploited

Confidentiality HighTotal information disclosure — all data in the component is compromised
Integrity HighTotal loss of integrity — attacker can modify any data in the component
Availability HighTotal denial of service — the component is completely unavailable