CVE-2023-20086: Cisco Adaptive Security Appliance Software

High severity, CVSS 8.6. EPSS: 0.7% chance of exploitation in the next 30 days.

A vulnerability in ICMPv6 processing of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition. This vulnerability is due to improper processing of ICMPv6 messages. An attacker could exploit this vulnerability by sending crafted ICMPv6 messages to a targeted Cisco ASA or FTD system with IPv6 enabled. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.

Affected products

• Cisco Adaptive Security Appliance Software: version 9.8.1 only; version 9.8.1.5 only; version 9.8.1.7 only; version 9.8.2 only; version 9.8.2.8 only; version 9.8.2.14 only; …
• Cisco Secure Firewall Threat Defense: version 6.2.3 only; version 6.2.3.1 only; version 6.2.3.2 only; version 6.2.3.3 only; version 6.2.3.4 only; version 6.2.3.5 only; …

Published 2023-11-01. Last modified 2026-08-11.