Multiple Denial of Service Vulnerabilities in Cisco Secure Firewall Products

• •Cisco disclosed multiple DoS vulnerabilities in its Secure Firewall products on September 16, 2026.
• •Unauthenticated remote attackers can exploit these vulnerabilities to cause device reloads and service disruptions.
• •Cisco has released patches for the vulnerabilities, but some lack workarounds.

On September 16, 2026, Cisco disclosed several denial of service (DoS) vulnerabilities affecting its Secure Firewall Adaptive Security Appliance (ASA) and Threat Defense (FTD) Software. These vulnerabilities allow unauthenticated remote attackers to cause devices to reload unexpectedly, leading to service disruptions. Specific attack vectors include improper rate limiting for syslog messages, buffer management issues in TLS 1.3, insufficient error checking in SSL VPN services, and improper resource management in EIGRP and DTLS message handling. Cisco has released software updates to address these vulnerabilities, but some have no workarounds. The affected systems include various Cisco Secure Firewall models, particularly those with specific configurations enabled. Security professionals are advised to apply the patches promptly to mitigate risks.