{"id":"CVE-2020-3555","title":"A vulnerability in the SIP inspection process of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a crash and reload of an affecte…","summary":"A vulnerability in the SIP inspection process of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a crash and reload of an affecte…","severity":"medium","cvss":6.8,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H","cwe":["CWE-404","CWE-404"],"vendor":"cisco","product":"adaptive_security_appliance","affected":["adaptive_security_appliance < 9.6.4.43","secure_firewall_threat_defense <= 6.2.2","secure_firewall_threat_defense >= 6.3.0, < 6.3.0.6","secure_firewall_threat_defense >= 6.4.0, < 6.4.0.10","secure_firewall_threat_defense >= 6.5.0, < 6.5.0.5","secure_firewall_threat_defense = 6.6.0","adaptive_security_appliance_software >= 9.7.0, < 9.8.4.24","adaptive_security_appliance_software >= 9.9.0, < 9.9.2.80","adaptive_security_appliance_software >= 9.10.0, < 9.10.1.43","adaptive_security_appliance_software >= 9.12.0, < 9.12.4.2","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 9.6.4.43","secure_firewall_threat_defense 6.5.0.5","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-2020-3555","references":[{"url":"https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-sipdos-3DGvdjvg","label":"psirt@cisco.com"},{"url":"https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-sipdos-3DGvdjvg","label":"af854a3a-2127-422b-91ae-364da2661108"}],"tags":["nvd"],"epss":0.01681,"epssPercentile":0.75543,"ingestedAt":"2026-08-11T19:48:28.809Z","slug":"CVE-2020-3555","body":"## Overview\n\nA vulnerability in the SIP inspection process of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a crash and reload of an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to a watchdog timeout and crash during the cleanup of threads that are associated with a SIP connection that is being deleted from the connection list. An attacker could exploit this vulnerability by sending a high rate of crafted SIP traffic through an affected device. A successful exploit could allow the attacker to cause a watchdog timeout and crash, resulting in a crash and reload of the affected device.\n\n## Affected\n\n- `adaptive_security_appliance < 9.6.4.43`\n- `secure_firewall_threat_defense <= 6.2.2`\n- `secure_firewall_threat_defense >= 6.3.0, < 6.3.0.6`\n- `secure_firewall_threat_defense >= 6.4.0, < 6.4.0.10`\n- `secure_firewall_threat_defense >= 6.5.0, < 6.5.0.5`\n- `secure_firewall_threat_defense = 6.6.0`\n- `adaptive_security_appliance_software >= 9.7.0, < 9.8.4.24`\n- `adaptive_security_appliance_software >= 9.9.0, < 9.9.2.80`\n- `adaptive_security_appliance_software >= 9.10.0, < 9.10.1.43`\n- `adaptive_security_appliance_software >= 9.12.0, < 9.12.4.2`\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 9.6.4.43`\n- `secure_firewall_threat_defense 6.5.0.5`\n- `adaptive_security_appliance_software 9.14.1.19`","depth":"sunlit","depthScore":38,"depthScoreParts":{"impact":37.4,"likelihood":0.3,"exploitation":0,"ransomware":0},"changes":[]}