CVE intelligenceCISA KEV

CVE-2026-20349

Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection Vulnerability

Published Aug 11, 2026Sources checked Oct 28, 2026

8.6HIGHCVSS out of 10

What this means

Actively exploited

CISA lists CVE-2026-20349 in its Known Exploited Vulnerabilities catalog, which means exploitation has been observed. The entry applies to Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD).

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

Public exploit: Not collected.

Cisco Security Advisories: Exploitation reported by Cisco Security Advisories (2026-09-16)
In August 2026, the Cisco PSIRT became aware of active exploitation of this vulnerability.

What to do next

Remediation and response

Review the linked vendor advisory and apply the mitigation or fixed release for your affected product.

Cisco Security Advisories guidance

Vendor revision: Sep 16, 2026

Cisco has released software updates that address this vulnerability.

CISA KEVListedObserved exploitation

EPSS1.0%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors1Source-linked actor relationships

Overview

What is 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.

Source: NVD

Reported activity: In August 2026, the Cisco PSIRT became aware of active exploitation of this vulnerability.
Cisco Security Advisories · Published Sep 16, 2026

CISA says:Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.CISA catalog due date Aug 14, 2026