Cisco Releases Security Updates for Secure Firewall ASA and Secure Firewall FTD Software

CVE-2026-20349 could allow unauthenticated remote attackers to trigger a denial-of-service condition on affected devices.

Threat ID:: CC-4831
Threat Severity:: Medium
Published:: 12 August 2026 2:07 PM

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Summary

CVE-2026-20349 could allow unauthenticated remote attackers to trigger a denial-of-service condition on affected devices.

Affected platforms

The following platforms are known to be affected:

Cisco Adaptive Security Appliance (ASA) Software

Cisco FirePower Threat Defense (FTD)

Threat details

Exploitation of CVE-2026-20349

Cisco has stated vulnerability CVE-2026-20349 has been observed exploited in the wild.

The NHS England National CSOC assesses further exploitation as likely.

Introduction

Cisco has released a security advisory to address a high severity vulnerability in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software.

CVE-2026-20349 - "Improper Disposal of Heap-Allocated Memory Before Release" vulnerability - CVSSv3.1 Score: 8.6

Remediation advice

Affected organisations are encouraged to review Cisco advisory cisco-sa-asaftd-vpn-dos-dzv4mQFF and apply the relevant update as soon as possible.

Organisations are encouraged to use the Cisco Software Checker tool to determine the latest available version for their deployment.

Definitive source of threat updates

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-dos-dzv4mQFF

CVE Vulnerabilities

Status Published

CVE-2026-20349

A vulnerability in the Remote Access SSL VPN service for Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition.  This vulnerability is due to insufficient error checking when processing HTTP requests. An attacker could exploit this vulnerability by sending a crafted HTTP request to the Remote Access SSL VPN service on an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition.

Last edited: 12 August 2026 2:07 pm