CVE-2026-20336

Cisco Secure Adaptive Security Appliance Software, Secure Firewall Threat Defense Software and Secure Firewall Management Center Software Hardening Release - Resource Lifetime Management Vulnerabilities

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

CVSS 3.18.8High EPSS percentile8th0.2% 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

Ask your IT provider to identify whether you run Cisco Secure Firewall Adaptive Security Appliance (ASA) Software, Cisco Secure Firewall Threat Defense (FTD) Software, or Cisco Secure Firewall Management Center (FMC).
Check Cisco’s security advisory and support portal for the affected-release list; the findings do not provide one.
No fixed version is currently available in the findings, so ask Cisco or your support provider for the hardening-release version and deployment plan.
Until Cisco provides the update, restrict management and firewall access to trusted, separated network segments and remove unnecessary access paths.

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-2026-20336 are related to issues concerning improper control of a resource through its lifetime that are grouped under the Common Weakness Enumeration (CWE) Pillar CWE-664.

In plain language

Written by AI from the record

Businesses using affected Cisco firewall or firewall-management software should treat this as urgent because public attack code is available and no fixed version is yet listed.

CVE-2026-20336 is a high-severity, unauthenticated adjacent-network resource-lifetime management vulnerability group affecting Cisco ASA, FTD, and FMC.

If you're affected

Firewall takeover
Network traffic exposure
Security-policy changes
Service disruption
Ransomware risk

What is it

This is a flaw in Cisco firewall software’s handling of resources while they are being used and cleaned up. Think of it like a building’s master-key system failing to take back a temporary key: someone on a connected network may be able to gain control, see protected information, alter settings, or interrupt service.

Who is affected

This matters if you run Cisco Secure Firewall Adaptive Security Appliance (ASA) Software, Cisco Secure Firewall Threat Defense (FTD) Software, or Cisco Secure Firewall Management Center (FMC). It is especially relevant for organizations that use these products to protect or manage important network connections. The issue is only reachable from an adjacent, connected network; no attacker login or user action is required.

How urgent is it

Public exploit code is available, so an attacker on a connected network can attempt to use this weakness now. Treat this as a red-priority issue: identify exposed systems immediately and apply Cisco’s hardening release as soon as its applicable version is confirmed.

What to do — in detail

Confirm whether ASA, FTD, or FMC is deployed and record each installed software release. Compare those releases with Cisco’s advisory once its affected-release and fixed-release tables are available; the supplied findings do not identify affected versions, fixed versions, or branch-specific targets.

No clean upgrade command or fixed-version target can be provided from these findings. Obtain the relevant Cisco hardening release from Cisco or an authorized support provider, review its release notes and compatibility requirements, stage it where possible, back up configuration, and deploy through the normal change process.

If patching is delayed, restrict device-management interfaces and other reachable services to required trusted network segments only, remove unnecessary adjacent-network connectivity, and review access-control rules. Monitor Cisco advisory updates, device-management access, unexpected configuration changes, firewall policy changes, service restarts, and unusual traffic from connected networks. CISA KEV does not list this CVE, so there is no KEV remediation due date.

Technical context

CVSS 3.1: 8.8 High (AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H). The weakness is CWE-664, improper control of a resource through its lifetime, grouped as multiple Cisco hardening-release vulnerabilities. The attack vector is adjacent network, with low attack complexity, no privileges, and no user interaction. Public exploit availability is reported; confirmed in-the-wild exploitation is not established by the supplied findings. CISA KEV does not list CVE-2026-20336. EPSS is 0.2% (10th percentile) with a flat trend; this is a prediction, not evidence of exploitation. Patch information, including fixed releases, is unavailable in the findings.

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.

EPSS8th

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 8th percentile of scored CVEs.

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

Lifecycle

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

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

Affected products

Ciscocommercial · USaka cisco systems, cisco systems inc.

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

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

Scored 8.8 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 UnchangedImpact is limited to the vulnerable component itself

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