{"id":"CVE-2026-20135","title":"A vulnerability in the TLS 1.3 implementation in Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an affected device to reload unexpectedly, resulting in a denial of service (Do…","summary":"A vulnerability in the TLS 1.3 implementation in Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an affected device to reload unexpectedly, resulting in a denial of service (Do…","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-415"],"vendor":"Cisco","product":"Cisco Secure Firewall Threat Defense (FTD) Software","affected":["secure_firewall_threat_defense_ftd_software 7.0.0","secure_firewall_threat_defense_ftd_software 7.0.0.1","secure_firewall_threat_defense_ftd_software 7.0.1","secure_firewall_threat_defense_ftd_software 7.0.1.1","secure_firewall_threat_defense_ftd_software 7.0.2","secure_firewall_threat_defense_ftd_software 7.2.0","secure_firewall_threat_defense_ftd_software 7.0.2.1","secure_firewall_threat_defense_ftd_software 7.0.3","secure_firewall_threat_defense_ftd_software 7.2.0.1","secure_firewall_threat_defense_ftd_software 7.0.4","secure_firewall_threat_defense_ftd_software 7.2.1","secure_firewall_threat_defense_ftd_software 7.0.5","secure_firewall_threat_defense_ftd_software 7.3.0","secure_firewall_threat_defense_ftd_software 7.2.2","secure_firewall_threat_defense_ftd_software 7.2.3","secure_firewall_threat_defense_ftd_software 7.3.1","secure_firewall_threat_defense_ftd_software 7.2.4","secure_firewall_threat_defense_ftd_software 7.0.6","secure_firewall_threat_defense_ftd_software 7.2.5","secure_firewall_threat_defense_ftd_software 7.2.4.1","secure_firewall_threat_defense_ftd_software 7.3.1.1","secure_firewall_threat_defense_ftd_software 7.4.0","secure_firewall_threat_defense_ftd_software 7.0.6.1","secure_firewall_threat_defense_ftd_software 7.2.5.1","secure_firewall_threat_defense_ftd_software 7.4.1","secure_firewall_threat_defense_ftd_software 7.2.6","secure_firewall_threat_defense_ftd_software 7.0.6.2","secure_firewall_threat_defense_ftd_software 7.4.1.1","secure_firewall_threat_defense_ftd_software 7.2.7","secure_firewall_threat_defense_ftd_software 7.2.5.2","secure_firewall_threat_defense_ftd_software 7.3.1.2","secure_firewall_threat_defense_ftd_software 7.2.8","secure_firewall_threat_defense_ftd_software 7.6.0","secure_firewall_threat_defense_ftd_software 7.4.2","secure_firewall_threat_defense_ftd_software 7.2.8.1","secure_firewall_threat_defense_ftd_software 7.0.6.3","secure_firewall_threat_defense_ftd_software 7.4.2.1","secure_firewall_threat_defense_ftd_software 7.2.9","secure_firewall_threat_defense_ftd_software 7.0.7","secure_firewall_threat_defense_ftd_software 7.7.0","secure_firewall_threat_defense_ftd_software 7.4.2.2","secure_firewall_threat_defense_ftd_software 7.2.10","secure_firewall_threat_defense_ftd_software 7.6.1","secure_firewall_threat_defense_ftd_software 7.4.2.3","secure_firewall_threat_defense_ftd_software 7.0.8","secure_firewall_threat_defense_ftd_software 7.6.2","secure_firewall_threat_defense_ftd_software 7.7.10","secure_firewall_threat_defense_ftd_software 7.7.11","secure_firewall_threat_defense_ftd_software 7.0.8.1","secure_firewall_threat_defense_ftd_software 7.6.2.1"],"published":"2026-09-16","updated":"2026-09-18","sourceUpdated":"2026-09-18T13:28:28.567","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-20135","references":[{"url":"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-tls1.3-dos-dLxwFWgF","label":"psirt@cisco.com"},{"url":"https://software.cisco.com"}],"tags":["nvd","cve.org","csaf","vendor-advisory","cisco"],"epss":0.00457,"epssPercentile":0.38963,"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"partial","timestamp":"2026-09-17T13:35:03.490455Z"},"ingestedAt":"2026-09-16T16:37:52.181Z","slug":"CVE-2026-20135","body":"## Overview\n\nA vulnerability in the TLS 1.3 implementation in Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an affected device to reload unexpectedly, resulting in a denial of service (DoS) condition.\r\n\r\nThis vulnerability is due to improper buffer management during the TLS 1.3 connection. An attacker could exploit this vulnerability by sending a crafted TLS 1.3 packet to an affected system through a TLS 1.3-enabled listening socket. A successful exploit could allow the attacker to cause the LINA process to crash, which would cause the device to reload. The reload can happen before or after authentication of the connection.Note: TLS 1.3 connections include both data traffic and user-management traffic.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **cisco-sa-ftd-tls1.3-dos-dLxwFWgF** · Cisco · affected: Cisco Firepower 2100 Series, Cisco Firepower 1000 Series, Cisco ASA 5500-X Series Firewalls, Cisco 3000 Series Industrial Security Appliances (ISA), Cisco Firepower 9000 Series, Cisco Firepower 4100 Series, … · updated 2026-09-16 · [advisory](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-tls1.3-dos-dLxwFWgF)","depth":"twilight","depthScore":47,"depthScoreParts":{"impact":47.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}