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CVE-2026-20021

MEDIUMCVSS 4.3/10EPSS 0.21%

Last modified

CVE-2026-20021 is a medium-severity vulnerability rated 4.3/10 on the CVSS scale. 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. EPSS estimates a 0.21% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
4.3/10

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS Probability
0.21%

11.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
CiscoAdaptive Security Appliance Software>= 9.12.1, <= 9.12.4.67
CiscoAdaptive Security Appliance Software>= 9.16.1, <= 9.16.4.85
CiscoAdaptive Security Appliance Software>= 9.17.1, <= 9.17.1.46
CiscoAdaptive Security Appliance Software>= 9.18.1, <= 9.18.4.68
CiscoAdaptive Security Appliance Software>= 9.19.1, <= 9.19.1.42
CiscoAdaptive Security Appliance Software>= 9.20.1, <= 9.20.4.14
CiscoAdaptive Security Appliance Software>= 9.22.1.1, <= 9.22.2.14
CiscoAdaptive Security Appliance Software>= 9.23.1, <= 9.23.1.22
CiscoFirepower Threat Defense Software6.4.0
CiscoFirepower Threat Defense Software6.4.0.1
CiscoFirepower Threat Defense Software6.4.0.2
CiscoFirepower Threat Defense Software6.4.0.3
CiscoFirepower Threat Defense Software6.4.0.4
CiscoFirepower Threat Defense Software6.4.0.5
CiscoFirepower Threat Defense Software6.4.0.6
CiscoFirepower Threat Defense Software6.4.0.7
CiscoFirepower Threat Defense Software6.4.0.8
CiscoFirepower Threat Defense Software6.4.0.9
CiscoFirepower Threat Defense Software6.4.0.10
CiscoFirepower Threat Defense Software6.4.0.11
CiscoFirepower Threat Defense Software6.4.0.12
CiscoFirepower Threat Defense Software6.4.0.13
CiscoFirepower Threat Defense Software6.4.0.14
CiscoFirepower Threat Defense Software6.4.0.15
CiscoFirepower Threat Defense Software6.4.0.16
CiscoFirepower Threat Defense Software6.4.0.17
CiscoFirepower Threat Defense Software6.4.0.18
CiscoFirepower Threat Defense Software7.0.0
CiscoFirepower Threat Defense Software7.0.0.1
CiscoFirepower Threat Defense Software7.0.1
CiscoFirepower Threat Defense Software7.0.1.1
CiscoFirepower Threat Defense Software7.0.2
CiscoFirepower Threat Defense Software7.0.2.1
CiscoFirepower Threat Defense Software7.0.3
CiscoFirepower Threat Defense Software7.0.4
CiscoFirepower Threat Defense Software7.0.5
CiscoFirepower Threat Defense Software7.0.6
CiscoFirepower Threat Defense Software7.0.6.1
CiscoFirepower Threat Defense Software7.0.6.2
CiscoFirepower Threat Defense Software7.0.6.3
CiscoFirepower Threat Defense Software7.0.7
CiscoFirepower Threat Defense Software7.0.8
CiscoFirepower Threat Defense Software7.0.8.1
CiscoFirepower Threat Defense Software7.1.0
CiscoFirepower Threat Defense Software7.1.0.1
CiscoFirepower Threat Defense Software7.1.0.2
CiscoFirepower Threat Defense Software7.1.0.3
CiscoFirepower Threat Defense Software7.2.0
CiscoFirepower Threat Defense Software7.2.0.1
CiscoFirepower Threat Defense Software7.2.1

Showing 50 of 84 affected configurations. See NVD for the full list.

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is 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 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.
How severe is CVE-2026-20021?
CVE-2026-20021 has a CVSS score of 4.3/10 (MEDIUM severity). The EPSS model estimates a 0.21% probability of exploitation in the next 30 days.
How do I fix CVE-2026-20021?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-20021?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST