CVE-2026-20335

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

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

CVSS 3.18.1High EPSS percentile18th0.3% 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 your organization runs Cisco Secure Firewall ASA, FTD, or FMC, including appliances managed by an IT provider.
Ask Cisco or your support provider whether your installed release is affected and whether any mitigation is available.
Cisco has not published a fixed version for CVE-2026-20335; apply Cisco’s release guidance as soon as it is issued.

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-2026-20335 are related to incorrect calculation issues that are grouped under the Common Weakness Enumeration (CWE) Pillar CWE-682.

In plain language

Written by AI from the record

A public attack method is available for Cisco Secure Firewall ASA, FTD, and FMC software, so businesses using these products should treat this as urgent; Cisco has not published a fixed version.

CVE-2026-20335 is a CVSS 8.1 network-reachable, unauthenticated vulnerability group involving incorrect calculations in Cisco Secure Firewall ASA, FTD, and FMC software.

If you're affected

Firewall management takeover
Network security disruption
Sensitive data exposure
Business service outages

What is it

This is a flaw in important Cisco firewall and firewall-management software. Think of it like an error in a building’s electronic access controls that could let someone interfere with locks, alarms, and the security office at the same time.

Who is affected

This matters to you if you run Cisco Secure Firewall ASA, FTD, or FMC software in your business or through a managed IT provider. It is especially relevant where those systems can be reached from the internet.

How urgent is it

A public exploit is available, meaning attackers have a working method they may adapt against exposed systems. Treat this as a red-priority issue: identify affected Cisco Secure Firewall systems now and obtain Cisco’s mitigation guidance while awaiting a fixed release.

What to do — in detail

Confirm the exact installed releases and deployment roles for Cisco Secure Firewall ASA, FTD, and FMC, then compare them with Cisco’s advisory when it becomes available. No affected-version range or fixed release has been provided, so there is no supported target version to recommend yet.

Until Cisco publishes a fix or workaround, reduce exposure by restricting administrative and management access to trusted networks and approved administrators, and remove unnecessary internet reachability. Review firewall and management-system logs for unexpected administrative access, configuration changes, or service interruptions. CISA has not added this CVE to the KEV catalog, so no CISA remediation due date applies.

Technical context

CVSS v3.1 is 8.1 (High): AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H. The reported weakness is CWE-682, incorrect calculation. A public exploit is available, but the CVE is not listed in CISA KEV and the supplied findings do not confirm exploitation in the wild. EPSS is 0.3% (21st percentile) with a flat trend. Patch and fixed-version information are not available.

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.

EPSS18th

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

0.3% chance of exploitation activity in the next 30 days, which ranks it in the 18th 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 updatedrecord updated, record 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:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Scored 8.1 by NVD.

How it is reached

Attack Vector NetworkExploitable remotely over the network without any special conditions
Attack Complexity HighRequires specific conditions like a race condition or non-default configuration
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