A vulnerability in the OSPF protocol of Cisco Secure Firewall ASA Software and Cisco Secure FTD Software could allow an unauthenticated, adjacent attacker to cause an affected device to reload unexpectedly, resulting in a DoS condition. If OSPF authentication is enabled, the attacker must know the secret key to exploit this vulnerability. This vulnerability is due to insufficient input validation when processing OSPF update packets. An attacker could exploit this vulnerability by sending crafted OSPF update packets. A successful exploit could allow the attacker to create a buffer overflow, causing the affected device to reload, resulting in a DoS condition.

A vulnerability in the OSPF protocol of Cisco Secure Firewall ASA Software and Cisco Secure FTD Software could allow an unauthenticated, adjacent attacker to cause an affected device to reload unexpectedly, resulting in a DoS condition. If OSPF authentication is enabled, the attacker must know the secret key to exploit this vulnerability. This vulnerability is due to insufficient input validation when processing OSPF update packets. An attacker could exploit this vulnerability by sending crafted OSPF update packets. A successful exploit could allow the attacker to create a buffer overflow, causing the affected device to reload, resulting in a DoS condition.

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According to its self-reported version, Cisco ASA Software is affected by multiple vulnerabilities.

Please see the included Cisco BIDs and Cisco Security Advisory for more information.

According to its self-reported version, Cisco Secure Firewall Threat Defense (FTD) Software is affected by multiple vulnerabilities.

Please see the included Cisco BIDs and Cisco Security Advisory for more information.

ID	Name	Product	Family	Type	Severity
506198	Cisco ASA Improper Input Validation (CVE-2026-20020)	Tenable OT Security	Tenable.ot	Remote	medium
311450	Cisco Adaptive Security Appliance (ASA) Software OSPF DoS Vulnerabilities (cisco-sa-asaftd-ospf-ZH8PhbSW)	Nessus	CISCO	Local	medium
311444	Cisco Firepower Threat Defense (FTD) Software OSPF DoS Vulnerabilities (cisco-sa-asaftd-ospf-ZH8PhbSW)	Nessus	CISCO	Combined	medium

Detections

Analytics

CVE-2026-20020

medium

Tenable Plugins

medium

medium

medium