CVE-2026-20331

Cisco Secure Adaptive Security Appliance Software, Secure Firewall Threat Defense Software and Secure Firewall Management Center Software Hardening Release - Protection Mechanism Failure Vulnerabilities

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

CVSS 3.19.6Critical EPSS percentile12th0.2% 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 Adaptive Security Appliance Software, Cisco Secure Firewall Threat Defense Software, or Cisco Secure Firewall Management Center Software.
Ask your Cisco support contact or managed IT provider whether your installed release is affected by CVE-2026-20331.
No fixed version has been published in the available findings; obtain Cisco's current remediation guidance before making upgrade changes.
Until guidance is available, limit access to the management and firewall interfaces to only required internal networks and approved administrators.

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

As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco Secure Adaptive Security Appliance Software, Cisco Secure Firewall Threat Defense Software and Cisco Secure Firewall Management Center Software engineering team has conducted a comprehensive internal security review. This review resulted in a software hardening release that addresses multiple internally discovered vulnerabilities.   The vulnerabilities tracked by CVE-2026-20331 are related to the failure of protection mechanisms issues that are grouped under the Common Weakness Enumeration (CWE) Pillar CWE-693.

In plain language

Written by AI from the record

This is a critical weakness in Cisco firewall and firewall-management software; small businesses using it should treat it as urgent because public attack code is available.

CVE-2026-20331 is a critical adjacent-network protection-mechanism failure affecting Cisco Secure Adaptive Security Appliance Software, Secure Firewall Threat Defense Software, and Secure Firewall Management Center Software.

If you're affected

Security-control bypass
Sensitive data exposure
Unauthorized configuration changes
Network service disruption

What is it

This is a flaw in protections meant to keep a firewall system from being misused. Think of it like a secure building whose locks are present but do not reliably stop someone using a known way around them, potentially exposing the network controls behind the door.

Who is affected

This matters to you if you run Cisco Secure Adaptive Security Appliance Software, Cisco Secure Firewall Threat Defense Software, or Cisco Secure Firewall Management Center Software. It is especially relevant where these systems can be reached from an adjacent network, such as another connected network segment.

How urgent is it

A public exploit is available, so treat this as a red, urgent issue and restrict unnecessary access now. CISA has not listed this CVE in its Known Exploited Vulnerabilities catalog, but that does not remove the need to assess and contain exposure promptly.

What to do — in detail

Confirm the installed product and release on every ASA, FTD, and FMC deployment, then identify interfaces reachable from adjacent network segments and any management paths exposed beyond their intended administrators. No fixed versions or patch details are available in the findings, so do not assume an upgrade target; obtain Cisco's current advisory or support guidance before changing releases.

If patching is delayed, restrict management and affected appliance interfaces to required network segments and approved administrator sources, remove unnecessary connectivity, and review firewall-management configuration changes for unexpected activity. No CISA KEV remediation due date applies because this CVE is not listed in KEV. Monitor Cisco advisories for fixed-release guidance and investigate unusual access attempts or unauthorized configuration changes.

Technical context

CVSS v3.1 is 9.6 (Critical): AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:L. The reported weakness is CWE-693, Protection Mechanism Failure. Public exploit code is available, indicating public exploit maturity; the findings do not confirm active exploitation. CISA KEV does not list this CVE. EPSS is 0.2% (14th percentile) with a flat trend; this is a prediction, not evidence of exploitation.

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.

EPSS12th

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

0.2% chance of exploitation activity in the next 30 days, which ranks it in the 12th percentile of scored CVEs.

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

Lifecycle

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

2026-09-18Record updated
2026-09-17Record updated
2026-09-16Publishedweakness classified, record updated

Affected products

Ciscocommercial · USaka cisco systems inc., cisco systems

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

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

Scored 9.6 by NVD.

How it is reached

Attack Vector AdjacentRequires access to the local network (e.g. same Wi-Fi, Bluetooth)
Attack Complexity LowNo special conditions — the attack can be reliably reproduced
Privileges Required NoneNo authentication required — anyone can exploit this
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 LowReduced performance or intermittent disruption of service