Vulnerability intelligence

CVE-2026-20221

Cisco Cisco Cyber Vision CWE-476

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.

CVSS Score

5.8

Medium

EPSS — Exploit Probability

0.5%

Riskier than 38% of all CVEs · checked 2026-10-22

Exploitation

Not in CISA KEV

KEV does not include every exploited vulnerability

Remediation

unknown

Check vendor advisories