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.
Timeline
- 2026-08-11Published to the U.S. National Vulnerability Database (NVD)
- 2026-08-11Added to the CISA Known Exploited Vulnerabilities (KEV) catalog
- 2026-08-14CISA federal remediation deadline (BOD 22-01)
CISA Known Exploited Vulnerability
Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection Vulnerability
Affected product
Cisco Secure Firewall Adaptive Security Appliance (ASA) And Secure Firewall Threat Defense (FTD)
Remediation Steps
- Apply Cisco security patches to Secure Firewall ASA and FTD devices immediately
- Monitor VPN traffic for denial-of-service attack patterns
- Restrict administrative access to firewall management interfaces
- Review firewall logs for exploit attempts
References
- https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-dos-dzv4mQFF
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-20349
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog
- https://nvd.nist.gov/vuln/detail/CVE-2026-20349
Referenced in our briefings & reports
- Vulnerability Priority Report – Week 2 of August 2026 (August 10 – 16)
Browse all tracked CVEs in the defend.network CVE database →