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CVE intelligence

CVE-2026-20043

Vulnerability intelligence

Published Oct 21, 2026Sources checked Oct 21, 2026
9.0CRITICALCVSS out of 10
What this means

Review the available evidence

CVE-2026-20043 and is rated Critical severity with a CVSS score of 9.0. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Cisco Security Advisories guidance

Vendor revision: Oct 21, 2026

To remediate the vulnerabilities that were disclosed on October 21, 2026, Cisco strongly recommends that customers upgrade to the fixed software that is indicated in the advisories.

Cisco Security Advisories guidance

Vendor revision: Oct 21, 2026

To assist customers in patching and to streamline the disclosure process, Cisco has grouped these issues by their underlying vulnerability class - Common Weakness Enumeration (CWE) - and assigned a single Common Vulnerabilities and Exposures Identifier (CVE ID) to each CWE grouping.

CISA KEVNot listedBased on the latest collected catalog
EPSSUnavailableNo current score collected
Ransomware useNot markedCISA KEV ransomware field
Threat actors0Source-linked actor relationships
Overview

What is CVE-2026-20043?

As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco owned Open Source Snort 3 Software engineering team has conducted a comprehensive internal security review. This review resulted in software hardening releases that address multiple internally discovered vulnerabilities.

The vulnerabilities tracked by CVE-2026-20043 are related to issues concerning out-of-bounds writes that are grouped under the Common Weakness Enumeration (CWE) Base CWE-787.

Source: NVD

Official advisory

Configuration and update guidance

Cisco Security Advisories · Updated Oct 21, 2026

Affected products and configuration

These vulnerabilities affect the following products, regardless of device configuration:

  • Cisco Cloud-delivered Firewall (CDFW)

  • Cisco Cyber Vision

  • Cisco Meraki MX Security Appliances

  • Cisco Secure Access (CSA)

  • Cisco Secure Firewall Threat Defense (FTD) Software

  • Open Source Snort 3

  • Unified Threat Defense (UTD) on Cisco IOS XE Software

For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.

Workarounds and temporary mitigations

There are no workarounds that address these vulnerabilities.

Fixed software

To remediate these vulnerabilities and avoid future exposure as described in this advisory, Cisco strongly recommends that customers upgrade to the fixed software indicated in this advisory.

Fixed Releases

The Cisco Product Security Incident Response Team (PSIRT) validates only the affected and fixed release information that is documented in this advisory.

For information about fixed releases, see the following sections.

Open Source Snort 3

The left column lists Snort software releases, and the right column indicates whether a release was affected by the vulnerability that is described in this advisory and which release included the fix for this vulnerability.

Snort 3 Release

First Fixed Release

3.x

3.12.4.0

Cyber Vision

In the following table, the left column lists Cisco software releases. The right column indicates whether a release is affected by the vulnerabilities that are described in this advisory and the first release that includes the fix for these vulnerabilities. Customers are advised to upgrade to an appropriate fixed software release as indicated in this section.

Cisco Cyber Vision Release

First Fixed Release

Earlier than 5.6

Migrate to a fixed release.

5.6

5.6.0

CDFW and CSA

Snort 3 is integrated natively into Cisco CDFW and CSA as part of the Snort 3 intrusion prevention system (IPS) technology to inspect traffic and block threats. No customer action is required. As of October 21, 2026, all Cisco CDFW and CSA cloud instances have been automatically updated with the Snort 3 package.

Meraki MX Security Appliances

Snort is integrated natively into Cisco Meraki security appliances as part of the threat protection services that are managed automatically through the Meraki Dashboard. No customer action is required to download Meraki firmware or the Snort 3 package for Meraki devices. As of October 21, 2026, all Meraki models listed in this advisory that are online and connected to the Cisco Meraki Dashboard have been automatically updated with the Snort 3 package.

Secure FTD Software

In the following table, the left column lists Cisco software releases. The right column indicates whether a release is affected by the vulnerabilities that are described in this advisory and the first release that includes the fix for these vulnerabilities. Customers are advised to upgrade to an appropriate fixed software release as indicated in this section.

Cisco Secure FTD Software Release

First Fixed Release

7.0 and earlier

7.0.10

7.2

7.2.12

7.4

7.4.8

7.6

7.6.6

7.7

7.7.13

10.0

10.0.2

10.1

10.1.0

UTD on Cisco IOS XE Software

In the following table, the left column lists Cisco software releases. The right column indicates whether a release is affected by the vulnerabilities that are described in this advisory and the first release that includes the fix for these vulnerabilities. Customers are advised to upgrade to an appropriate fixed software release as indicated in this section.

Cisco IOS XE Software Release

First Fixed Release

17.12

17.12.8

17.15

17.15.6

17.18

17.18.5

26.1

26.1.2

26.2

26.2.1

Exploitation status

The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerabilities that are described in this advisory.

Read the collected advisory