CVE-2021-1573: Cisco Adaptive Security Appliance

High severity, CVSS 7.5. EPSS: 1.3% chance of exploitation in the next 30 days.

A vulnerability in the web services interface of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to trigger a denial of service (DoS) condition. This vulnerability is due to improper input validation when parsing HTTPS requests. An attacker could exploit this vulnerability by sending a malicious HTTPS request to an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.

Affected products

• Cisco Adaptive Security Appliance: up to and including 9.7
• Cisco Adaptive Security Appliance Software: from 9.8, before 9.8.4.40 (fixed in 9.8.4.40); from 9.9, before 9.12.4.26 (fixed in 9.12.4.26); from 9.13, before 9.14.3 (fixed in 9.14.3); from 9.15, before 9.15.1.17 (fixed in 9.15.1.17); from 9.16, before 9.16.1.28 (fixed in 9.16.1.28)
• Cisco Secure Firewall Threat Defense: up to and including 6.2.2; from 6.2.3, before 6.4.0.13 (fixed in 6.4.0.13); from 6.5.0, before 6.6.5 (fixed in 6.6.5); from 6.7.0, before 6.7.0.3 (fixed in 6.7.0.3); version 7.0.0 only

Published 2022-01-11. Last modified 2026-08-11.