CVE-2026-20221 Multiple Cisco Products Snort 3 Generic Routing Encapsulation Denial of Service Vulnerabilities
- Exploited in the wild
- Not known
- Fix
- None listed
What is CVE-2026-20221?
CVE-2026-20221 is a medium-severity vulnerability in Cisco Cyber Vision, published on 21 Oct 2026.
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.
Weakness: CWE-476
Which versions are affected by CVE-2026-20221?
How do I fix CVE-2026-20221?
No fix has been published for CVE-2026-20221 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-20221 being exploited?
There is no known exploitation of CVE-2026-20221 in the wild and no public exploit code.
Sources
Also known as GHSA-vm6m-qmxg-cg2c.