All vulnerabilities
CVE-2026-20221

Multiple Cisco Products Snort 3 Generic Routing Encapsulation Denial of Service Vulnerabilities

Cisco Cisco Cyber VisionNetwork & edge
Open in ThreatlineRecord JSON
CVSS
5.8Medium
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.45%Chance of exploitation activity in the next 30 days, higher than 38% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed inNone listedNo source names a fixed version. Check the vendor advisory below
Published21 Oct 2026Updated 22 Oct 2026CVE List

What fixes it

No source in this snapshot names a fixed version. The vendor advisories under References are the place to check.

Vendor and government advisories 1

Vendors that say their products are affected, and agencies that issued alerts. Check each for the fixed release of the product you run.

Reports 2

1 outlet mention it. Reports are not confirmation; each links to its source.

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.

Text from CVE List

Affected versions 150

  • Cisco Cyber Visionaffected: 3.0.0CVE List
  • Cisco Cyber Visionaffected: 3.0.2CVE List
  • Cisco Cyber Visionaffected: 3.0.3CVE List
  • Cisco Cyber Visionaffected: 3.0.1CVE List
  • Cisco Cyber Visionaffected: 3.1.0CVE List
  • Cisco Cyber Visionaffected: 3.0.4CVE List
  • Cisco Cyber Visionaffected: 3.1.1CVE List
  • Cisco Cyber Visionaffected: 3.1.2CVE List
  • Cisco Cyber Visionaffected: 3.2.0CVE List
  • Cisco Cyber Visionaffected: 3.0.5CVE List
  • Cisco Cyber Visionaffected: 3.2.1CVE List
  • Cisco Cyber Visionaffected: 3.0.6CVE List
  • Cisco Cyber Visionaffected: 3.2.2CVE List
  • Cisco Cyber Visionaffected: 3.2.3CVE List
  • Cisco Cyber Visionaffected: 3.2.4CVE List
  • Cisco Cyber Visionaffected: 4.0.0CVE List
  • Cisco Cyber Visionaffected: 4.0.1CVE List
  • Cisco Cyber Visionaffected: 4.0.2CVE List
  • Cisco Cyber Visionaffected: 4.0.3CVE List
  • Cisco Cyber Visionaffected: 4.1.0CVE List
  • Cisco Cyber Visionaffected: 4.1.1CVE List
  • Cisco Cyber Visionaffected: 4.1.2CVE List
  • Cisco Cyber Visionaffected: 4.1.3CVE List
  • Cisco Cyber Visionaffected: 4.1.4CVE List
  • Cisco Cyber Visionaffected: 4.2.0CVE List
  • Cisco Cyber Visionaffected: 4.2.1CVE List
  • Cisco Cyber Visionaffected: 4.1.5CVE List
  • Cisco Cyber Visionaffected: 4.2.2CVE List
  • Cisco Cyber Visionaffected: 4.2.XCVE List
  • Cisco Cyber Visionaffected: 4.2.3CVE List
  • Cisco Open Source Snort3affected: 3.12.2.0CVE List
  • Cisco Open Source Snort3affected: 3.1.2.0CVE List
  • Cisco Open Source Snort3affected: 3.1.3.0CVE List
  • Cisco Open Source Snort3affected: 3.1.4.0CVE List
  • Cisco Open Source Snort3affected: 3.1.5.0CVE List
  • Cisco Open Source Snort3affected: 3.1.6.0CVE List
  • Cisco Open Source Snort3affected: 3.1.7.0CVE List
  • Cisco Open Source Snort3affected: 3.1.8.0CVE List
  • Cisco Open Source Snort3affected: 3.1.9.0CVE List
  • Cisco Open Source Snort3affected: 3.1.10.0CVE List
  • Cisco Open Source Snort3affected: 3.1.12.0CVE List
  • Cisco Open Source Snort3affected: 3.1.13.0CVE List
  • Cisco Open Source Snort3affected: 3.1.14.0CVE List
  • Cisco Open Source Snort3affected: 3.1.15.0CVE List
  • Cisco Open Source Snort3affected: 3.1.16.0CVE List
  • Cisco Open Source Snort3affected: 3.1.17.0CVE List
  • Cisco Open Source Snort3affected: 3.1.18.0CVE List
  • Cisco Open Source Snort3affected: 3.1.19.0CVE List
  • Cisco Open Source Snort3affected: 3.1.20.0CVE List
  • Cisco Open Source Snort3affected: 3.1.21.0CVE List
  • Cisco Open Source Snort3affected: 3.1.22.0CVE List
  • Cisco Open Source Snort3affected: 3.1.23.0CVE List
  • Cisco Open Source Snort3affected: 3.1.24.0CVE List
  • Cisco Open Source Snort3affected: 3.1.25.0CVE List
  • Cisco Open Source Snort3affected: 3.1.27.0CVE List
  • Cisco Open Source Snort3affected: 3.1.28.0CVE List
  • Cisco Open Source Snort3affected: 3.1.29.0CVE List
  • Cisco Open Source Snort3affected: 3.1.30.0CVE List
  • Cisco Open Source Snort3affected: 3.1.31.0CVE List
  • Cisco Open Source Snort3affected: 3.1.32.0CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.0.0CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.0.0.1CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.0.1CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.0.1.1CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.0.2CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.2.0CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.0.2.1CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.0.3CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.2.0.1CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.0.4CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.2.1CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.0.5CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.3.0CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.2.2CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.2.3CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.3.1CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.2.4CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.0.6CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.2.5CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.2.4.1CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.3.1.1CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.4.0CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.0.6.1CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.2.5.1CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.4.1CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.2.6CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.0.6.2CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.4.1.1CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.2.7CVE List
  • Cisco Secure Firewall Threat Defense (FTD) Softwareaffected: 7.2.5.2CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.6.0CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.5.6CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.5CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.4.12CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.7CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.6.2CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.5.5CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.5.4CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.8CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.6.1CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.5.7CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 1.5.4CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 1.5.5CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 1.5.6CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.0.0CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.0.2CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.0.3CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.1.0CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.1.2CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.1.4CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.1.5CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.2CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.2.1CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.3CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.3.1CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.4CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.4.4CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.4.6CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 2.8.9CVE List
  • Cisco Umbrella Insights Virtual Applianceaffected: 3.0CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: 3.17.1SCVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: 16.12.3CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: Fuji-16.9.5CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: 16.12.4CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: 17.3.1aCVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: 16.6.6CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: 16.12.2CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: Fuji-16.9.6CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: 3.17.0SCVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: Fuji-16.9.3CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: Denali-16.3.7CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: Fuji-16.9.2CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: Fuji-16.9.4CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: Everest-16.6.4CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: Everest-16.6.3CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: 16.6.5CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: Denali-16.3.5CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: 17.2.1rCVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: 17.1.1CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: Everest-16.6.2CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: 16.6.7aCVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: Denali-16.3.4CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: 16.6.1CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: Denali-16.3.9CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: Denali-16.3.3CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: 16.12.1aCVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: 17.3.2CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: 17.4.1aCVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: 16.12.5CVE List
  • Cisco UTD SNORT IPS Engine Softwareaffected: 17.5.1CVE List

References 1