cisco-sa-asaftd-vpn-dos-dzv4mQFFHighCVSS 8.6

Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software Remote Access SSL VPN Denial of Service Vulnerability

Published
August 11, 2026
Last Modified
September 16, 2026

🔗 CVE IDs covered (1)

CVE-2026-20349 →

📋 Description

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.

Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.

This advisory is part of a group of advisories. For a complete list of the advisories and links to them, see Cisco Advance Notification for Publication of September 16, 2026, Security Advisories ["https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-notice-jfxK98ZP"]. In addition, for further documentation of improvements and fixes in Cisco Secure Firewall products, see Cisco Secure Firewall Adaptive Security Appliance Software, Secure Firewall Threat Defense Software, and Secure Firewall Management Center Software Hardening Release: September 2026 ["https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-hardening-asaftdfmc-uvpPROhN"].

CVE-2026-20349 — Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software Remote Access SSL VPN Denial of Service Vulnerability (CVSS 3.1 8.6, CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H)

🎯 Affected products209

  • Cisco 3000 Series Industrial Security Appliances (ISA)
  • Cisco ASA 5500-X Series Firewalls
  • Cisco Adaptive Security Virtual Appliance (ASAv)
  • Cisco Firepower 1000 Series
  • Cisco Firepower 2100 Series
  • Cisco Firepower 4100 Series
  • Cisco Firepower 9000 Series
  • Cisco Secure Firewall 1200 Series
  • Cisco Secure Firewall 200 Series
  • Cisco Secure Firewall 3100 Series
  • Cisco Secure Firewall 4200 Series
  • Cisco Secure Firewall 6100 Series
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
  • Cisco Secure Firewall Threat Defense (FTD) Software
  • Cisco Secure Firewall Threat Defense Virtual
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.1
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.1.28
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.2
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.2.11
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.2.13
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.2.14
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.2.3
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.2.7
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.3
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.3.14
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.3.15
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.3.19
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.3.23
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.3.3
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.4
  • +179 more not shown

✅ Remediation

Cisco has released software updates that address this vulnerability. https://software.cisco.com Workarounds: There are no workarounds that address this vulnerability.

🔗 References (7)