CVE-2021-1573: Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software Web Services Denial of Service Vulnerability

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2022-01-11 · updated 2026-08-11
Weakness: CWE-121

Description

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: through 9.7
Cisco ASA Software: from 9.8 before 9.8.4.40; from 9.9 before 9.12.4.26; from 9.13 before 9.14.3; from 9.15 before 9.15.1.17; from 9.16 before 9.16.1.28 — fixed in 9.12.4.26, 9.14.3, 9.15.1.17, 9.16.1.28, 9.8.4.40
Cisco Firepower Threat Defense Software: through 6.2.2; from 6.2.3 before 6.4.0.13; from 6.5.0 before 6.6.5; from 6.7.0 before 6.7.0.3; 7.0.0 — fixed in 6.4.0.13, 6.6.5, 6.7.0.3

How to fix

Upgrade to a fixed version: Cisco ASA Software 9.12.4.26, 9.14.3, 9.15.1.17, 9.16.1.28; Cisco Firepower Threat Defense Software 6.4.0.13, 6.6.5, 6.7.0.3. Check the vendor advisory for mitigations.

References

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