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.

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Changed

Confidentiality Impact None

Integrity Impact None

Availability Impact Low

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00454.

Exploitation none

Automatable yes

Technical Impact partial

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
Cisco Cisco Cyber Vision unknown
Version Status Constraints
3.0.0 affected —
3.0.2 affected —
3.0.3 affected —
3.0.1 affected —
3.1.0 affected —
3.0.4 affected —
3.1.1 affected —
3.1.2 affected —
3.2.0 affected —
3.0.5 affected —
3.2.1 affected —
3.0.6 affected —
3.2.2 affected —
3.2.3 affected —
3.2.4 affected —
4.0.0 affected —
4.0.1 affected —
4.0.2 affected —
4.0.3 affected —
4.1.0 affected —
4.1.1 affected —
4.1.2 affected —
4.1.3 affected —
4.1.4 affected —
4.2.0 affected —
4.2.1 affected —
4.1.5 affected —
4.2.2 affected —
4.2.X affected —
4.2.3 affected —
4.2.4 affected —
4.2.6 affected —
4.1.6 affected —
4.3.0 affected —
4.3.1 affected —
4.3.2 affected —
4.3.3 affected —
4.4.0 affected —
4.4.1 affected —
4.4.2 affected —
4.4.3 affected —
4.1.7 affected —
5.0.0 affected —
5.0.1 affected —
5.0.2 affected —
5.1.0 affected —
5.1.1 affected —
5.1.2 affected —
5.1.3 affected —
5.2.0 affected —
5.2.1 affected —
5.3.0 affected —
5.3.1 affected —
5.3.2 affected —
5.3.3 affected —
5.5.1 affected —
5.6.1 affected —
5.6.0 affected —
5.4.0 affected —
5.4.1 affected —
5.4.2 affected —
Cisco Cisco Open Source Snort3 unknown
Version Status Constraints
3.12.2.0 affected —
3.1.2.0 affected —
3.1.3.0 affected —
3.1.4.0 affected —
3.1.5.0 affected —
3.1.6.0 affected —
3.1.7.0 affected —
3.1.8.0 affected —
3.1.9.0 affected —
3.1.10.0 affected —
3.1.12.0 affected —
3.1.13.0 affected —
3.1.14.0 affected —
3.1.15.0 affected —
3.1.16.0 affected —
3.1.17.0 affected —
3.1.18.0 affected —
3.1.19.0 affected —
3.1.20.0 affected —
3.1.21.0 affected —
3.1.22.0 affected —
3.1.23.0 affected —
3.1.24.0 affected —
3.1.25.0 affected —
3.1.27.0 affected —
3.1.28.0 affected —
3.1.29.0 affected —
3.1.30.0 affected —
3.1.31.0 affected —
3.1.32.0 affected —
3.1.36.0 affected —
3.1.38.0 affected —
3.1.39.0 affected —
3.1.40.0 affected —
3.1.41.0 affected —
3.1.42.0 affected —
3.1.43.0 affected —
3.1.45.0 affected —
3.1.47.0 affected —
3.1.48.0 affected —
3.1.50.0 affected —
3.1.51.0 affected —
3.1.52.0 affected —
3.1.53.0 affected —
3.1.55.0 affected —
3.1.56.0 affected —
3.1.57.0 affected —
3.1.58.0 affected —
3.1.59.0 affected —
3.1.60.0 affected —
3.1.61.0 affected —
3.1.62.0 affected —
3.1.63.0 affected —
3.1.64.0 affected —
3.1.65.0 affected —
3.1.66.0 affected —
3.1.67.0 affected —
3.1.69.0 affected —
3.1.70.0 affected —
3.1.71.0 affected —
3.1.72.0 affected —
3.1.73.0 affected —
3.1.74.0 affected —
3.1.75.0 affected —
3.1.76.0 affected —
3.1.77.0 affected —
3.1.78.0 affected —
3.1.81.0 affected —
3.1.82.0 affected —
3.1.83.0 affected —
3.1.84.0 affected —
3.2.1.0 affected —
3.2.2.0 affected —
3.3.0.0 affected —
3.3.1.0 affected —
3.3.2.0 affected —
3.3.3.0 affected —
3.3.4.0 affected —
3.3.5.0 affected —
3.3.7.0 affected —
3.5.0.0 affected —
3.5.1.0 affected —
3.8.1.0 affected —
3.6.0.0 affected —
3.6.2.0 affected —
3.9.3.0 affected —
3.7.2.0 affected —
3.7.0.0 affected —
3.9.6.0 affected —
3.10.0.0 affected —
3.10.2.0 affected —
3.7.4.0 affected —
3.9.0.0 affected —
3.5.2.0 affected —
3.12.1.0 affected —
3.6.1.0 affected —
3.9.2.0 affected —
3.6.3.0 affected —
3.9.5.0 affected —
3.7.1.0 affected —
3.9.7.0 affected —
3.7.3.0 affected —
3.10.1.0 affected —
3.9.1.0 affected —
3.11.1.0 affected —
Cisco Cisco Secure Firewall Threat Defense (FTD) Software unknown
Version Status Constraints
7.0.0 affected —
7.0.0.1 affected —
7.0.1 affected —
7.0.1.1 affected —
7.0.2 affected —
7.2.0 affected —
7.0.2.1 affected —
7.0.3 affected —
7.2.0.1 affected —
7.0.4 affected —
7.2.1 affected —
7.0.5 affected —
7.3.0 affected —
7.2.2 affected —
7.2.3 affected —
7.3.1 affected —
7.2.4 affected —
7.0.6 affected —
7.2.5 affected —
7.2.4.1 affected —
7.3.1.1 affected —
7.4.0 affected —
7.0.6.1 affected —
7.2.5.1 affected —
7.4.1 affected —
7.2.6 affected —
7.0.6.2 affected —
7.4.1.1 affected —
7.2.7 affected —
7.2.5.2 affected —
7.3.1.2 affected —
7.2.8 affected —
7.6.0 affected —
7.4.2 affected —
7.2.8.1 affected —
7.0.6.3 affected —
7.4.2.1 affected —
7.2.9 affected —
7.0.7 affected —
7.7.0 affected —
7.4.2.2 affected —
7.2.10 affected —
7.6.1 affected —
7.4.2.3 affected —
7.0.8 affected —
7.6.2 affected —
7.7.10 affected —
7.7.11 affected —
7.0.8.1 affected —
7.6.2.1 affected —
7.7.10.1 affected —
7.4.2.4 affected —
7.2.10.2 affected —
7.4.3 affected —
7.6.4 affected —
10.0.0 affected —
7.4.4 affected —
7.0.9 affected —
7.2.11 affected —
7.4.7 affected —
Cisco Cisco Umbrella Insights Virtual Appliance unknown
Version Status Constraints
2.6.0 affected —
2.5.6 affected —
2.5 affected —
2.4.12 affected —
2.7 affected —
2.6.2 affected —
2.5.5 affected —
2.5.4 affected —
2.8 affected —
2.6.1 affected —
2.5.7 affected —
1.5.4 affected —
1.5.5 affected —
1.5.6 affected —
2.0.0 affected —
2.0.2 affected —
2.0.3 affected —
2.1.0 affected —
2.1.2 affected —
2.1.4 affected —
2.1.5 affected —
2.2 affected —
2.2.1 affected —
2.3 affected —
2.3.1 affected —
2.4 affected —
2.4.4 affected —
2.4.6 affected —
2.8.9 affected —
3.0 affected —
3.1 affected —
3.2 affected —
2.8.1 affected —
2.8.2 affected —
2.8.3 affected —
2.8.4 affected —
2.8.5 affected —
3.0.1 affected —
3.0.2 affected —
3.0.4 affected —
3.0.5 affected —
3.1.1 affected —
3.1.2 affected —
3.1.3 affected —
3.1.4 affected —
3.2.1 affected —
3.2.2 affected —
3.2.3 affected —
3.3 affected —
3.3.1 affected —
3.3.2 affected —
3.3.3 affected —
3.3.4 affected —
3.4 affected —
3.4.1 affected —
3.4.2 affected —
3.4.3 affected —
3.4.4 affected —
3.4.5 affected —
3.4.6 affected —
3.5 affected —
2.7.1 affected —
2.7.2 affected —
2.7.6 affected —
2.7.9 affected —
2.7.10 affected —
3.5.1 affected —
3.5.2 affected —
3.6.1 affected —
3.6.2 affected —
3.7 affected —
3.7.1 affected —
3.8.3 affected —
Cisco Cisco UTD SNORT IPS Engine Software unknown
Version Status Constraints
3.17.1S affected —
16.12.3 affected —
Fuji-16.9.5 affected —
16.12.4 affected —
17.3.1a affected —
16.6.6 affected —
16.12.2 affected —
Fuji-16.9.6 affected —
3.17.0S affected —
Fuji-16.9.3 affected —
Denali-16.3.7 affected —
Fuji-16.9.2 affected —
Fuji-16.9.4 affected —
Everest-16.6.4 affected —
Everest-16.6.3 affected —
16.6.5 affected —
Denali-16.3.5 affected —
17.2.1r affected —
17.1.1 affected —
Everest-16.6.2 affected —
16.6.7a affected —
Denali-16.3.4 affected —
16.6.1 affected —
Denali-16.3.9 affected —
Denali-16.3.3 affected —
16.12.1a affected —
17.3.2 affected —
17.4.1a affected —
16.12.5 affected —
17.5.1 affected —
Fuji-16.9.7 affected —
16.6.9 affected —
17.3.3 affected —
17.5.1a affected —
17.3.4 affected —
17.3.4a affected —
17.4.2 affected —
17.4.1b affected —
17.6.1a affected —
16.6.10 affected —
17.7.1a affected —
16.12.6 affected —
Fuji-16.9.8 affected —
17.6.2 affected —
17.8.1a affected —
16.12.7 affected —
17.3.5 affected —
17.6.3 affected —
17.6.3a affected —
17.7.2 affected —
17.9.1a affected —
17.6.4 affected —
17.10.1a affected —
17.3.6 affected —
16.12.8 affected —
17.3.7 affected —
17.9.2a affected —
17.6.5 affected —
17.11.1a affected —
17.9.3a affected —
17.12.1a affected —
17.9.4 affected —
17.6.6 affected —
17.3.8 affected —
17.3.8a affected —
17.6.6a affected —
17.9.4a affected —
17.12.2 affected —
17.13.1a affected —
17.9.5a affected —
17.12.3 affected —
17.6.7 affected —
17.14.1a affected —
17.12.4 affected —
17.12.3a affected —
17.15.1a affected —
17.6.8 affected —
17.9.6 affected —
17.6.8a affected —
17.16.1a affected —
17.9.5e affected —
17.12.4a affected —
17.15.2c affected —
17.9.5f affected —
17.12.4b affected —
17.15.2a affected —
17.12.5 affected —
17.17.1 affected —
17.12.5a affected —
17.9.7a affected —
17.15.3a affected —
17.15.3 affected —
17.12.5b affected —
17.12.5c affected —
17.15.4 affected —
17.9.7b affected —
17.18.1 affected —
17.18.1a affected —
17.12.6 affected —
17.9.8 affected —
17.15.4c affected —
17.12.5d affected —
17.18.2 affected —
26.1.1 affected —
17.15.5 affected —
17.15.5a affected —
17.12.7 affected —
17.12.7a affected —
17.12.7b affected —
17.9.9 affected —
17.18.3a affected —
17.12.8 affected —
17.15.6 affected —
17.18.4 affected —
26.1.2 affected —
17.9.10 affected —

No data.

No data.

OpenCVE Enrichment is a feature of OpenCVE that uses AI to automatically link vendors and products to CVEs. Learn more on GitHub.

Vendors Products
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Cisco Utd Snort Ips Engine Software Subscribe
Cyber Vision Subscribe
Secure Firewall Threat Defense Subscribe
Umbrella Insights Virtual Appliance Subscribe

Project Subscriptions

Vendors Products
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Cisco Utd Snort Ips Engine Software Subscribe
Cyber Vision Subscribe
Secure Firewall Threat Defense Subscribe
Umbrella Insights Virtual Appliance Subscribe
Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort3-gre-JNpMHrTv cve-icon cve-icon
History

Fri, 23 Oct 2026 00:45:00 +0000

Type Values Removed Values Added
First Time appeared Cisco
Cisco cisco Open Source Snort3
Cisco cisco Secure Firewall Threat Defense (ftd) Software
Cisco cisco Utd Snort Ips Engine Software
Cisco cyber Vision
Cisco secure Firewall Threat Defense
Cisco umbrella Insights Virtual Appliance
Vendors & Products Cisco
Cisco cisco Open Source Snort3
Cisco cisco Secure Firewall Threat Defense (ftd) Software
Cisco cisco Utd Snort Ips Engine Software
Cisco cyber Vision
Cisco secure Firewall Threat Defense
Cisco umbrella Insights Virtual Appliance

Thu, 22 Oct 2026 14:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Wed, 21 Oct 2026 17:15:00 +0000

Type Values Removed Values Added
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.
Title Multiple Cisco Products Snort 3 Generic Routing Encapsulation Denial of Service Vulnerabilities
Weaknesses CWE-476
References
Metrics cvssV3_1

{'score': 5.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: cisco

Published:

Updated: 2026-10-22T19:11:26.546Z

Reserved: 2025-10-08T11:59:15.398Z

Link: CVE-2026-20221

cve-icon Vulnrichment

Updated: 2026-10-22T13:36:52.741Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-10-21T17:18:27.947

Modified: 2026-10-22T14:17:40.940

Link: CVE-2026-20221

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-22T20:30:12Z

Weaknesses