CVE-2026-20023 Cisco CVE debrief

Who should care

Network administrators and security teams responsible for managing Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software should be aware of this vulnerability and take necessary actions to mitigate it.

Technical summary

The vulnerability is due to memory corruption when parsing OSPF protocol packets. An attacker could exploit this vulnerability by sending crafted OSPF packets to an affected device. A successful exploit could allow the attacker to cause memory corruption causing the affected device to reboot, resulting in a denial of service (DoS) condition. This issue affects Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software. Network administrators should review the official advisory for specific affected versions and take necessary actions to mitigate the vulnerability. The priority for defensive actions is medium to high due to the potential for denial of service attacks. The CVE record was published on 2026-03-04T19:16:14.627Z and has not been modified since then. The NVD entry is currently Analyzed. To address this vulnerability, it is crucial to apply patches or updates provided by Cisco and implement compensating controls such as monitoring and filtering OSPF protocol packets. Additionally, restricting access to affected devices and networks can help mitigate the risk. The evidence for this CVE is based on the official CVE record and the NVD detail page. The technical details provided are based on the available information from these sources, and further updates may be necessary as more information becomes available. Affected organizations should prioritize patching and consider additional security measures to protect against potential exploitation. The vulnerability highlights the importance of keeping software up-to-date and having robust security measures in place to prevent and respond to potential threats. Cisco's official advisory should be consulted for detailed information on affected products, versions, and recommended actions. The CVSS score for this vulnerability is 6.1, indicating a medium severity level. However, the actual impact may vary depending on the specific environment and implementation. Therefore, it is essential to carefully evaluate the vulnerability and implement appropriate measures to mitigate its effects. By taking proactive steps, organizations can reduce the risk of a DoS

Defensive priority

The priority for defensive actions is medium to high due to the potential for denial of service attacks.

Recommended defensive actions

• Inventory and verify affected Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software versions.
• Apply patches or updates provided by Cisco to address the vulnerability.
• Implement compensating controls such as monitoring and filtering OSPF protocol packets.
• Restrict access to affected devices and networks.
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance.
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed.

Evidence notes

The evidence for this CVE is based on the official CVE record and the NVD detail page. The CVE record was published on 2026-03-04T19:16:14.627Z and has not been modified since then. The NVD entry is currently Analyzed.

Official resources