Resource exhaustion in Cisco Adaptive Security Appliance (ASA) and Cisco Firewall Threat Defense (FTD) - CVE-2026-20021
Published: March 9, 2026
Vulnerability identifier: #VU123658
CSH Severity: Medium
CVSS v4: 6 [CVSS:4.0/AV:A/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-20021
CWE-ID: CWE-400
Exploitation vector: Adjecent network
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to application does not properly control consumption of internal resources when handling OSPF packets. A remote attacker on the local network can send specially crafted OSPF packets to an affected device, trigger memory exhaustion and perform a denial of service (DoS) attack.
Affected software
Cisco Adaptive Security Appliance (ASA)
Cisco Firewall Threat Defense (FTD)
Cisco Firewall Threat Defense (FTD)
How to mitigate CVE-2026-20021
Install updates from vendor's website.
Cisco Adaptive Security Appliance (ASA) - addressed in versions 9.16.4.89, 9.18.4.71, 9.20.4.19, 9.22.2.20, 9.23.1.26, 9.24.1
Cisco Firewall Threat Defense (FTD) - addressed in versions 7.0.9, 7.2.11, 7.4.4, 7.6.4, 7.7.11
Cisco Firewall Threat Defense (FTD) - addressed in versions 7.0.9, 7.2.11, 7.4.4, 7.6.4, 7.7.11