Cisco patches firewall zero day exploited to cause remote crashes

Hackers are actively exploiting a high severity zero day vulnerability in Cisco firewall appliances to crash targeted devices, CSO Online reported. The flaw affects the Remote Access SSL VPN service of Cisco Secure Firewall Adaptive Security Appliance and Cisco Secure Firewall Threat Defense. [1]

According to CSO Online, Cisco identified the flaw as CVE-2026-76418, assigning it a severity rating of 8.6. The issue stems from logic errors that occur when secondary authentication is configured on a tunnel group. Unauthenticated remote attackers can trigger the crash by sending a crafted request when connecting to the SSL remote access VPN. [1]

Cisco has released patches to address the flaw, CSO Online reported. There are no available workarounds to prevent exploitation. Cisco is an American technology conglomerate based in San Jose, California, that develops networking hardware and cybersecurity software. [1][2]

The targeting of network edge infrastructure follows similar campaigns against other security platforms. As FTMQ Security reported earlier, vendors including Citrix and Palo Alto Networks issued emergency updates in October 2026 for zero day vulnerabilities in NetScaler and PAN-OS products that were subjected to active attacks. [3][4]