{"id":"CVE-2020-3571","title":"A vulnerability in the ICMP ingress packet processing of Cisco Firepower Threat Defense (FTD) Software for Cisco Firepower 4110 appliances could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an…","summary":"A vulnerability in the ICMP ingress packet processing of Cisco Firepower Threat Defense (FTD) Software for Cisco Firepower 4110 appliances could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an…","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-20"],"vendor":"cisco","product":"secure_firewall_threat_defense","affected":["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"],"patched":["secure_firewall_threat_defense 6.5.0.5"],"published":"2020-10-21","updated":"2026-08-11","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2020-3571","references":[{"url":"https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-icmp-dos-hxxcycM","label":"psirt@cisco.com"},{"url":"https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-icmp-dos-hxxcycM","label":"af854a3a-2127-422b-91ae-364da2661108"}],"tags":["nvd"],"epss":0.01374,"epssPercentile":0.70374,"ingestedAt":"2026-08-18T12:28:06.386Z","slug":"CVE-2020-3571","body":"## Overview\n\nA vulnerability in the ICMP ingress packet processing of Cisco Firepower Threat Defense (FTD) Software for Cisco Firepower 4110 appliances could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to incomplete input validation upon receiving ICMP packets. An attacker could exploit this vulnerability by sending a high number of crafted ICMP or ICMPv6 packets to an affected device. A successful exploit could allow the attacker to cause a memory exhaustion condition that may result in an unexpected reload. No manual intervention is needed to recover the device after the reload.\n\n## Affected\n\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\n## Remediation\n\nUpgrade past the affected range:\n\n- `secure_firewall_threat_defense 6.5.0.5`","depth":"twilight","depthScore":48,"depthScoreParts":{"impact":47.3,"likelihood":0.3,"exploitation":0,"ransomware":0},"changes":[]}