---
title: "CVE-2026-20349: Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection Vulnerability"
url: https://erroneo.us/security/cve/CVE-2026-20349/
description: "CVE-2026-20349 (Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD)): Exploited in the wild (CISA KEV). A…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-08-11
date_modified: 2026-09-16
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-20349"
kev: true
cvss: 8.6
epss: 0.0101
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-20349: Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection Vulnerability

**Signal:** Exploited: patch now if you run it. CISA has confirmed exploitation in the wild. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Yes, if you run Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD). CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-08-11, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-08-14 ; treat that as the outer limit, not the target.
- EPSS 1.0% , percentile 63: FIRST’s model estimates a 1.0% chance of exploitation activity in the next 30 days, higher than 63% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Editorial verdict: Patch this week. Cisco ASA/FTD CVE-2026-20349: Exploited VPN Crash Bug — If your ASA or FTD terminates remote access VPN, SSL VPN or ZTNA, install the fixed release this week; attackers are using this to knock firewalls offline, but Cisco describes no code execution or data theft.

## What it is

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.

## Affected products (CVE record)

- Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software: 9.16.1, 9.16.1.28, 9.16.2, 9.16.2.3, 9.16.2.7, 9.16.2.11, 9.16.2.13, 9.16.2.14, 9.16.3.3, 9.16.3, 9.16.3.14, 9.18.1
- Cisco Cisco Secure Firewall Threat Defense (FTD) Software: 7.0.0, 7.0.0.1, 7.0.1, 7.0.1.1, 7.0.2, 7.2.0, 7.0.2.1, 7.0.3, 7.2.0.1, 7.0.4, 7.2.1, 7.0.5

## Severity

- cisco CVSS 3.1: 8.6 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H`

## Exploitation

- CISA KEV: added 2026-08-11; federal due date 2026-08-14. Known ransomware use: Unknown.
- CISA required action: 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 SSVC assessment: exploitation active , automatable yes , technical impact partial .
- FIRST EPSS (model of 2026-10-21): 1.01% probability of exploitation activity in the next 30 days; percentile 63.

## Sources

- [Listed in CISA KEV notes (sec.cloudapps.cisco.com)](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-dos-dzv4mQFF)
- [CVE.org record CVE-2026-20349](https://www.cve.org/CVERecord?id=CVE-2026-20349)
- [NVD entry CVE-2026-20349](https://nvd.nist.gov/vuln/detail/CVE-2026-20349)
- [CISA Known Exploited Vulnerabilities catalog entry](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-20349)
- [Listed in CISA KEV notes (cisa.gov)](https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk)
- [Listed in CISA KEV notes (cisa.gov)](https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk)

---
Source page: https://erroneo.us/security/cve/CVE-2026-20349/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt