Vulnerability · Published Oct 21, 2026 · Assigned by cisco
CVE-2026-20221Multiple Cisco Products Snort 3 Generic Routing Encapsulation Denial of Service Vulnerabilities
Medium 5.8
In plain English
A medium-severity null pointer dereference in Cisco Cyber Vision from Cisco. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 48% of all known vulnerabilities).
Official description
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Cisco | Cisco Cyber Vision | 3.0.03.0.23.0.33.0.13.1.03.0.43.1.13.1.2 |
| Cisco | Cisco Open Source Snort3 | 3.12.2.03.1.2.03.1.3.03.1.4.03.1.5.03.1.6.03.1.7.03.1.8.0 |
| Cisco | Cisco Secure Firewall Threat Defense (FTD) Software | 7.0.07.0.0.17.0.17.0.1.17.0.27.2.07.0.2.17.0.3 |
| Cisco | Cisco Umbrella Insights Virtual Appliance | 2.6.02.5.62.52.4.122.72.6.22.5.52.5.4 |
| Cisco | Cisco UTD SNORT IPS Engine Software | 3.17.1S16.12.3Fuji-16.9.516.12.417.3.1a16.6.616.12.2Fuji-16.9.6 |
Weakness: CWE-476 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L