Medium severity · published Mar 4, 2026
CVE-2026-20021
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…
4.3
CVSS
0.2%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack vector
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 10% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CS
Cisco Secure Firewall Adaptive Security Appliance (ASA) Software · Cisco
9.12.1; 9.12.1.2; 9.12.1.3; 9.12.2; 9.12.2.4; 9.12.2.5; +34 more · source: vendor
CS
Cisco Secure Firewall Threat Defense (FTD) Software · Cisco
6.4.0; 6.4.0.1; 6.4.0.3; 6.4.0.2; 6.4.0.4; 6.4.0.5; +34 more · source: vendor
AS
Adaptive Security Appliance Software · Cisco
9.12.1 through 9.12.4.67; 9.16.1 through 9.16.4.85; 9.17.1 through 9.17.1.46; 9.18.1 through 9.18.4.68; 9.19.1 through 9.19.1.42; 9.20.1 through 9.20.4.14; +2 more · source: NVD
SF
Secure Firewall Threat Defense · Cisco
6.4.0; 6.4.0.1; 6.4.0.2; 6.4.0.3; 6.4.0.4; 6.4.0.5; +34 more · source: NVD
Affected product
CS
Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
Cisco
More from Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
9.9
CVE-2025-20333
Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow Vulnerability
8.6
CVE-2026-20349
Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software Remote Access SSL VPN Denial of Service Vulnerability
8.6
CVE-2025-20362
Cisco Secure Firewall Adaptive Security (ASA) Appliance and Secure Firewall Threat Defense (FTD) Missing Authorization Vulnerability
9.9
CVE-2026-20332
Cisco Secure Adaptive Security Appliance Software, Secure Firewall Threat Defense Software and Secure Firewall Management Center Software Hardening Release - Improper Access Control Vulnerabilities
9.9
CVE-2026-20330
Cisco Secure Adaptive Security Appliance Software, Secure Firewall Threat Defense Software and Secure Firewall Management Center Software Hardening Release - Improper Neutralization Vulnerabilities