CVE-2026-20221
Multiple Cisco Products Snort 3 Generic Routing Encapsulation Denial of Service Vulnerabilities
CVSS Score
5.8
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-476 |
| Vendor | cisco |
| Product | cisco cyber vision |
| Ecosystems | |
| Industries | NetworkingTelecommunications |
| Published | Oct 21, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
Low
Affected Versions
Cisco / Cisco Cyber Vision
3.0.0 3.0.2 3.0.3 3.0.1 3.1.0 3.0.4 3.1.1 3.1.2 3.2.0 3.0.5 3.2.1 3.0.6 3.2.2 3.2.3 3.2.4 4.0.0 4.0.1 4.0.2 4.0.3 4.1.0 4.1.1 4.1.2 4.1.3 4.1.4 4.2.0 4.2.1 4.1.5 4.2.2 4.2.X 4.2.3 4.2.4 4.2.6 4.1.6 4.3.0 4.3.1 4.3.2 4.3.3 4.4.0 4.4.1 4.4.2 4.4.3 4.1.7 5.0.0 5.0.1 5.0.2 5.1.0 5.1.1 5.1.2 5.1.3 5.2.0 5.2.1 5.3.0 5.3.1 5.3.2 5.3.3 5.5.1 5.6.1 5.6.0 5.4.0 5.4.1 5.4.2
Cisco / Cisco Open Source Snort3
3.12.2.0 3.1.2.0 3.1.3.0 3.1.4.0 3.1.5.0 3.1.6.0 3.1.7.0 3.1.8.0 3.1.9.0 3.1.10.0 3.1.12.0 3.1.13.0 3.1.14.0 3.1.15.0 3.1.16.0 3.1.17.0 3.1.18.0 3.1.19.0 3.1.20.0 3.1.21.0 3.1.22.0 3.1.23.0 3.1.24.0 3.1.25.0 3.1.27.0 3.1.28.0 3.1.29.0 3.1.30.0 3.1.31.0 3.1.32.0 3.1.36.0 3.1.38.0 3.1.39.0 3.1.40.0 3.1.41.0 3.1.42.0 3.1.43.0 3.1.45.0 3.1.47.0 3.1.48.0 3.1.50.0 3.1.51.0 3.1.52.0 3.1.53.0 3.1.55.0 3.1.56.0 3.1.57.0 3.1.58.0 3.1.59.0 3.1.60.0 3.1.61.0 3.1.62.0 3.1.63.0 3.1.64.0 3.1.65.0 3.1.66.0 3.1.67.0 3.1.69.0 3.1.70.0 3.1.71.0 3.1.72.0 3.1.73.0 3.1.74.0 3.1.75.0 3.1.76.0 3.1.77.0 3.1.78.0 3.1.81.0 3.1.82.0 3.1.83.0 3.1.84.0 3.2.1.0 3.2.2.0 3.3.0.0 3.3.1.0 3.3.2.0 3.3.3.0 3.3.4.0 3.3.5.0 3.3.7.0 3.5.0.0 3.5.1.0 3.8.1.0 3.6.0.0 3.6.2.0 3.9.3.0 3.7.2.0 3.7.0.0 3.9.6.0 3.10.0.0 3.10.2.0 3.7.4.0 3.9.0.0 3.5.2.0 3.12.1.0 3.6.1.0 3.9.2.0 3.6.3.0 3.9.5.0 3.7.1.0 3.9.7.0 3.7.3.0 3.10.1.0 3.9.1.0 3.11.1.0
Cisco / Cisco Secure Firewall Threat Defense (FTD) Software
7.0.0 7.0.0.1 7.0.1 7.0.1.1 7.0.2 7.2.0 7.0.2.1 7.0.3 7.2.0.1 7.0.4 7.2.1 7.0.5 7.3.0 7.2.2 7.2.3 7.3.1 7.2.4 7.0.6 7.2.5 7.2.4.1 7.3.1.1 7.4.0 7.0.6.1 7.2.5.1 7.4.1 7.2.6 7.0.6.2 7.4.1.1 7.2.7 7.2.5.2 7.3.1.2 7.2.8 7.6.0 7.4.2 7.2.8.1 7.0.6.3 7.4.2.1 7.2.9 7.0.7 7.7.0 7.4.2.2 7.2.10 7.6.1 7.4.2.3 7.0.8 7.6.2 7.7.10 7.7.11 7.0.8.1 7.6.2.1 7.7.10.1 7.4.2.4 7.2.10.2 7.4.3 7.6.4 10.0.0 7.4.4 7.0.9 7.2.11 7.4.7
Cisco / Cisco Umbrella Insights Virtual Appliance
2.6.0 2.5.6 2.5 2.4.12 2.7 2.6.2 2.5.5 2.5.4 2.8 2.6.1 2.5.7 1.5.4 1.5.5 1.5.6 2.0.0 2.0.2 2.0.3 2.1.0 2.1.2 2.1.4 2.1.5 2.2 2.2.1 2.3 2.3.1 2.4 2.4.4 2.4.6 2.8.9 3.0 3.1 3.2 2.8.1 2.8.2 2.8.3 2.8.4 2.8.5 3.0.1 3.0.2 3.0.4 3.0.5 3.1.1 3.1.2 3.1.3 3.1.4 3.2.1 3.2.2 3.2.3 3.3 3.3.1 3.3.2 3.3.3 3.3.4 3.4 3.4.1 3.4.2 3.4.3 3.4.4 3.4.5 3.4.6 3.5 2.7.1 2.7.2 2.7.6 2.7.9 2.7.10 3.5.1 3.5.2 3.6.1 3.6.2 3.7 3.7.1 3.8.3
Cisco / Cisco UTD SNORT IPS Engine Software
3.17.1S 16.12.3 Fuji-16.9.5 16.12.4 17.3.1a 16.6.6 16.12.2 Fuji-16.9.6 3.17.0S Fuji-16.9.3 Denali-16.3.7 Fuji-16.9.2 Fuji-16.9.4 Everest-16.6.4 Everest-16.6.3 16.6.5 Denali-16.3.5 17.2.1r 17.1.1 Everest-16.6.2 16.6.7a Denali-16.3.4 16.6.1 Denali-16.3.9 Denali-16.3.3 16.12.1a 17.3.2 17.4.1a 16.12.5 17.5.1 Fuji-16.9.7 16.6.9 17.3.3 17.5.1a 17.3.4 17.3.4a 17.4.2 17.4.1b 17.6.1a 16.6.10 17.7.1a 16.12.6 Fuji-16.9.8 17.6.2 17.8.1a 16.12.7 17.3.5 17.6.3 17.6.3a 17.7.2 17.9.1a 17.6.4 17.10.1a 17.3.6 16.12.8 17.3.7 17.9.2a 17.6.5 17.11.1a 17.9.3a 17.12.1a 17.9.4 17.6.6 17.3.8 17.3.8a 17.6.6a 17.9.4a 17.12.2 17.13.1a 17.9.5a 17.12.3 17.6.7 17.14.1a 17.12.4 17.12.3a 17.15.1a 17.6.8 17.9.6 17.6.8a 17.16.1a 17.9.5e 17.12.4a 17.15.2c 17.9.5f 17.12.4b 17.15.2a 17.12.5 17.17.1 17.12.5a 17.9.7a 17.15.3a 17.15.3 17.12.5b 17.12.5c 17.15.4 17.9.7b 17.18.1 17.18.1a 17.12.6 17.9.8 17.15.4c 17.12.5d 17.18.2 26.1.1 17.15.5 17.15.5a 17.12.7 17.12.7a 17.12.7b 17.9.9 17.18.3a 17.12.8 17.15.6 17.18.4 26.1.2 17.9.10