CVE-2020-3562: Cisco Secure Firewall Threat Defense

High severity, CVSS 8.6. EPSS: 1.8% chance of exploitation in the next 30 days.

A vulnerability in the SSL/TLS inspection of Cisco Firepower Threat Defense (FTD) Software for Cisco Firepower 2100 Series firewalls could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to improper input validation for certain fields of specific SSL/TLS messages. An attacker could exploit this vulnerability by sending a malformed SSL/TLS message through an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition. No manual intervention is needed to recover the device after it has reloaded.

Affected products

• Cisco Secure Firewall Threat Defense: version 6.3.0 only; version 6.4.0 only; version 6.5.0 only

Published 2020-10-21. Last modified 2026-08-11.