CVE-2026-20221
No fix known EPSS <1%CVSS 5.8
Multiple Cisco products are affected by a vulnerability in the generic routing encapsulation (GRE) tunnel decapsulation feature of the Snort 3 Detection Engine that could allow an unauthenticated, remote attacker to cause an unexpected restart of the Snort 3 Detection Engine. This vulnerability is due to improper handling of nested GRE traffic. An attacker could exploit this vulnerability by sending a crafted GRE payload through an affected device. A successful exploit could allow the attacker to trigger an unexpected reload of the Snort 3 Detection Engine, resulting in either a bypass or denial of service (DoS) condition, depending on device configuration. For more information, see the section of this advisory. The Snort 3 Detection Engine will restart automatically. No manual intervention is required.
Products: Cisco Cyber Vision, Cisco Open Source Snort3, Cisco Secure Firewall Threat Defense (FTD) Software, Cisco Umbrella Insights Virtual Appliance, Cisco UTD SNORT IPS Engine Software