{"id":"CVE-2020-3572","title":"A vulnerability in the SSL/TLS session handler of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condi…","summary":"A vulnerability in the SSL/TLS session handler of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condi…","severity":"high","cvss":8.6,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H","cwe":["CWE-400","CWE-401"],"vendor":"cisco","product":"adaptive_security_appliance","affected":["adaptive_security_appliance < 9.6","secure_firewall_threat_defense < 6.3.0.6","secure_firewall_threat_defense >= 6.4.0, < 6.4.0.10","secure_firewall_threat_defense >= 6.5.0, < 6.6.1","adaptive_security_appliance_software >= 9.8.0, < 9.8.4.26","adaptive_security_appliance_software >= 9.9.0, < 9.9.2.80","adaptive_security_appliance_software >= 9.10.0, < 9.10.1.44","adaptive_security_appliance_software >= 9.12.0, < 9.12.4.4","adaptive_security_appliance_software >= 9.13.0, < 9.13.1.13","adaptive_security_appliance_software >= 9.14.0, < 9.14.1.19"],"patched":["adaptive_security_appliance 9.6","secure_firewall_threat_defense 6.6.1","adaptive_security_appliance_software 9.14.1.19"],"published":"2020-10-21","updated":"2026-08-11","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2020-3572","references":[{"url":"https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asa-ftd-tcp-dos-N3DMnU4T","label":"psirt@cisco.com"},{"url":"https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asa-ftd-tcp-dos-N3DMnU4T","label":"af854a3a-2127-422b-91ae-364da2661108"}],"tags":["nvd"],"epss":0.01778,"epssPercentile":0.76918,"ingestedAt":"2026-08-18T12:28:06.425Z","slug":"CVE-2020-3572","body":"## Overview\n\nA vulnerability in the SSL/TLS session handler of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to a memory leak when closing SSL/TLS connections in a specific state. An attacker could exploit this vulnerability by establishing several SSL/TLS sessions and ensuring they are closed under certain conditions. A successful exploit could allow the attacker to exhaust memory resources in the affected device, which would prevent it from processing new SSL/TLS connections, resulting in a DoS. Manual intervention is required to recover an affected device.\n\n## Affected\n\n- `adaptive_security_appliance < 9.6`\n- `secure_firewall_threat_defense < 6.3.0.6`\n- `secure_firewall_threat_defense >= 6.4.0, < 6.4.0.10`\n- `secure_firewall_threat_defense >= 6.5.0, < 6.6.1`\n- `adaptive_security_appliance_software >= 9.8.0, < 9.8.4.26`\n- `adaptive_security_appliance_software >= 9.9.0, < 9.9.2.80`\n- `adaptive_security_appliance_software >= 9.10.0, < 9.10.1.44`\n- `adaptive_security_appliance_software >= 9.12.0, < 9.12.4.4`\n- `adaptive_security_appliance_software >= 9.13.0, < 9.13.1.13`\n- `adaptive_security_appliance_software >= 9.14.0, < 9.14.1.19`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `adaptive_security_appliance 9.6`\n- `secure_firewall_threat_defense 6.6.1`\n- `adaptive_security_appliance_software 9.14.1.19`","depth":"twilight","depthScore":48,"depthScoreParts":{"impact":47.3,"likelihood":0.4,"exploitation":0,"ransomware":0},"changes":[]}