A critical zero-day vulnerability, tracked as CVE-2026-20349, has been discovered in Cisco's Secure Firewall ASA and FTD devices, allowing remote attackers to launch denial-of-service (DoS) attacks without requiring authentication. This flaw can be exploited by sending specially crafted requests to the affected devices, potentially causing them to become unresponsive. Cisco has released patches to address this issue, which is currently being actively discussed, with the company determining the exploitation status to decide whether immediate patching is necessary or if monitoring is sufficient1. The vulnerability is considered high-risk due to its ability to be exploited remotely, and its presence in critical network infrastructure. This vulnerability matters to security practitioners because it highlights the importance of prompt patching and monitoring of critical infrastructure devices to prevent potential disruptions to business operations.