CVE-2026-20021: Medium severity Cisco Secure Firewall Adaptive Security Appliance (ASA) Software vulnerability

Published Mar 4, 2026
·
Updated

A vulnerability in the OSPF protocol of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an authenticated, adjacent attacker to exhaust memory on an affected device, resulting in a denial of service (DoS) condition. This vulnerability is due to improperly validating input by the OSPF protocol when parsing packets. An attacker could exploit this vulnerability by by sending crafted OSPF packets to an affected device. A successful exploit could allow the attacker to exhaust memory on the affected device, resulting in a DoS condition.

Affected Software

86 affected components
Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
Cisco Secure Firewall Threat Defense (FTD) Software
Cisco Adaptive Security Appliance Software>=9.12.1<=9.12.4.67
Cisco Adaptive Security Appliance Software>=9.16.1<=9.16.4.85
Cisco Adaptive Security Appliance Software>=9.17.1<=9.17.1.46
Cisco Adaptive Security Appliance Software>=9.18.1<=9.18.4.68
Cisco Adaptive Security Appliance Software>=9.19.1<=9.19.1.42
Cisco Adaptive Security Appliance Software>=9.20.1<=9.20.4.14
Cisco Adaptive Security Appliance Software>=9.22.1.1<=9.22.2.14
Cisco Adaptive Security Appliance Software>=9.23.1<=9.23.1.22
Cisco Secure Firewall Threat Defense=6.4.0
Cisco Secure Firewall Threat Defense=6.4.0.1
Cisco Secure Firewall Threat Defense=6.4.0.2
Cisco Secure Firewall Threat Defense=6.4.0.3
Cisco Secure Firewall Threat Defense=6.4.0.4
Cisco Secure Firewall Threat Defense=6.4.0.5
Cisco Secure Firewall Threat Defense=6.4.0.6
Cisco Secure Firewall Threat Defense=6.4.0.7
Cisco Secure Firewall Threat Defense=6.4.0.8
Cisco Secure Firewall Threat Defense=6.4.0.9
Cisco Secure Firewall Threat Defense=6.4.0.10
Cisco Secure Firewall Threat Defense=6.4.0.11
Cisco Secure Firewall Threat Defense=6.4.0.12
Cisco Secure Firewall Threat Defense=6.4.0.13
Cisco Secure Firewall Threat Defense=6.4.0.14
Cisco Secure Firewall Threat Defense=6.4.0.15
Cisco Secure Firewall Threat Defense=6.4.0.16
Cisco Secure Firewall Threat Defense=6.4.0.17
Cisco Secure Firewall Threat Defense=6.4.0.18
Cisco Secure Firewall Threat Defense=7.0.0
Cisco Secure Firewall Threat Defense=7.0.0.1
Cisco Secure Firewall Threat Defense=7.0.1
Cisco Secure Firewall Threat Defense=7.0.1.1
Cisco Secure Firewall Threat Defense=7.0.2
Cisco Secure Firewall Threat Defense=7.0.2.1
Cisco Secure Firewall Threat Defense=7.0.3
Cisco Secure Firewall Threat Defense=7.0.4
Cisco Secure Firewall Threat Defense=7.0.5
Cisco Secure Firewall Threat Defense=7.0.6
Cisco Secure Firewall Threat Defense=7.0.6.1
Cisco Secure Firewall Threat Defense=7.0.6.2
Cisco Secure Firewall Threat Defense=7.0.6.3
Cisco Secure Firewall Threat Defense=7.0.7
Cisco Secure Firewall Threat Defense=7.0.8
Cisco Secure Firewall Threat Defense=7.0.8.1
Cisco Secure Firewall Threat Defense=7.1.0
Cisco Secure Firewall Threat Defense=7.1.0.1
Cisco Secure Firewall Threat Defense=7.1.0.2
Cisco Secure Firewall Threat Defense=7.1.0.3
Cisco Secure Firewall Threat Defense=7.2.0
Cisco Secure Firewall Threat Defense=7.2.0.1
Cisco Secure Firewall Threat Defense=7.2.1
Cisco Secure Firewall Threat Defense=7.2.2
Cisco Secure Firewall Threat Defense=7.2.3
Cisco Secure Firewall Threat Defense=7.2.4
Cisco Secure Firewall Threat Defense=7.2.4.1
Cisco Secure Firewall Threat Defense=7.2.5
Cisco Secure Firewall Threat Defense=7.2.5.1
Cisco Secure Firewall Threat Defense=7.2.5.2
Cisco Secure Firewall Threat Defense=7.2.6
Cisco Secure Firewall Threat Defense=7.2.7
Cisco Secure Firewall Threat Defense=7.2.8
Cisco Secure Firewall Threat Defense=7.2.8.1
Cisco Secure Firewall Threat Defense=7.2.9
Cisco Secure Firewall Threat Defense=7.2.10
Cisco Secure Firewall Threat Defense=7.2.10.2
Cisco Secure Firewall Threat Defense=7.3.0
Cisco Secure Firewall Threat Defense=7.3.1
Cisco Secure Firewall Threat Defense=7.3.1.1
Cisco Secure Firewall Threat Defense=7.3.1.2
Cisco Secure Firewall Threat Defense=7.4.0
Cisco Secure Firewall Threat Defense=7.4.1
Cisco Secure Firewall Threat Defense=7.4.1.1
Cisco Secure Firewall Threat Defense=7.4.2
Cisco Secure Firewall Threat Defense=7.4.2.1
Cisco Secure Firewall Threat Defense=7.4.2.2
Cisco Secure Firewall Threat Defense=7.4.2.3
Cisco Secure Firewall Threat Defense=7.4.2.4
Cisco Secure Firewall Threat Defense=7.4.3
Cisco Secure Firewall Threat Defense=7.6.0
Cisco Secure Firewall Threat Defense=7.6.1
Cisco Secure Firewall Threat Defense=7.6.2
Cisco Secure Firewall Threat Defense=7.6.2.1
Cisco Secure Firewall Threat Defense=7.7.0
Cisco Secure Firewall Threat Defense=7.7.10
Cisco Secure Firewall Threat Defense=7.7.10.1

Event History

Mar 4, 2026
CVE Published
via MITRE·06:35 PM
Data Sourced
via MITRE·06:35 PM
DescriptionSeverityWeakness
Data Sourced
via NVD·07:16 PM
DescriptionSeverityWeaknessAffected Software
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Frequently Asked Questions

1

What is the severity of CVE-2026-20021?

CVE-2026-20021 is considered a high severity vulnerability due to its potential to cause denial of service on affected devices.

2

How do I fix CVE-2026-20021?

To mitigate CVE-2026-20021, it is recommended to update Cisco Secure Firewall Adaptive Security Appliance and Cisco Secure Firewall Threat Defense Software to the latest version provided by Cisco.

3

What devices are affected by CVE-2026-20021?

CVE-2026-20021 affects Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software.

4

What can an attacker achieve with CVE-2026-20021?

An authenticated, adjacent attacker can exploit CVE-2026-20021 to exhaust memory on the device, leading to a denial of service condition.

5

Is CVE-2026-20021 remote or local attack vector?

CVE-2026-20021 requires local access as it is an authenticated vulnerability affecting adjacent devices.

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