{"id":"CVE-2020-3255","title":"A vulnerability in the packet processing functionality of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device","summary":"A vulnerability in the packet processing functionality of 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…","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-400","CWE-400"],"vendor":"cisco","product":"secure_firewall_threat_defense","affected":["secure_firewall_threat_defense >= 6.2.3, < 6.2.3.16","secure_firewall_threat_defense >= 6.3.0, < 6.3.0.6","secure_firewall_threat_defense >= 6.4.0, < 6.4.0.9","asa_5505_firmware = 9.10(1.3)","asa_5510_firmware = 9.10(1.3)","asa_5512-x_firmware = 9.10(1.3)","asa_5515-x_firmware = 9.10(1.3)","asa_5520_firmware = 9.10(1.3)","asa_5525-x_firmware = 9.10(1.3)","asa_5540_firmware = 9.10(1.3)","asa_5545-x_firmware = 9.10(1.3)","asa_5550_firmware = 9.10(1.3)","asa_5555-x_firmware = 9.10(1.3)","asa_5580_firmware = 9.10(1.3)","asa_5585-x_firmware = 9.10(1.3)"],"patched":["secure_firewall_threat_defense 6.4.0.9"],"published":"2020-05-06","updated":"2026-08-11","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2020-3255","references":[{"url":"https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-dos-N2vQZASR","label":"psirt@cisco.com"},{"url":"https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-dos-N2vQZASR","label":"af854a3a-2127-422b-91ae-364da2661108"}],"tags":["nvd"],"epss":0.0184,"epssPercentile":0.77717,"ingestedAt":"2026-08-11T19:48:27.714Z","slug":"CVE-2020-3255","body":"## Overview\n\nA vulnerability in the packet processing functionality of 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 inefficient memory management. An attacker could exploit this vulnerability by sending a high rate of IPv4 or IPv6 traffic through an affected device. This traffic would need to match a configured block action in an access control policy. An exploit could allow the attacker to cause a memory exhaustion condition on the affected device, which would result in a DoS for traffic transiting the device, as well as sluggish performance of the management interface. Once the flood is stopped, performance should return to previous states.\n\n## Affected\n\n- `secure_firewall_threat_defense >= 6.2.3, < 6.2.3.16`\n- `secure_firewall_threat_defense >= 6.3.0, < 6.3.0.6`\n- `secure_firewall_threat_defense >= 6.4.0, < 6.4.0.9`\n- `asa_5505_firmware = 9.10(1.3)`\n- `asa_5510_firmware = 9.10(1.3)`\n- `asa_5512-x_firmware = 9.10(1.3)`\n- `asa_5515-x_firmware = 9.10(1.3)`\n- `asa_5520_firmware = 9.10(1.3)`\n- `asa_5525-x_firmware = 9.10(1.3)`\n- `asa_5540_firmware = 9.10(1.3)`\n- `asa_5545-x_firmware = 9.10(1.3)`\n- `asa_5550_firmware = 9.10(1.3)`\n- `asa_5555-x_firmware = 9.10(1.3)`\n- `asa_5580_firmware = 9.10(1.3)`\n- `asa_5585-x_firmware = 9.10(1.3)`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `secure_firewall_threat_defense 6.4.0.9`","depth":"twilight","depthScore":42,"depthScoreParts":{"impact":41.3,"likelihood":0.4,"exploitation":0,"ransomware":0},"changes":[]}