CVE-2026-20221
Multiple Cisco Products Snort 3 Generic Routing Encapsulation Denial of Service Vulnerabilities
- Published
- Updated
- Reserved
- Assigned by
- cisco
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.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| ciscoCNA (assigner) | 3.1 | Medium5.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L |
| NVDNVD · Awaiting Analysis | 3.1 | Medium5.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L |
- EPSS (exploitation in 30 days)
- 0.58% · top 52% of all CVEs (6 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: yes · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.8.
Weakness
Affected products
- affected 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
- and 21 more
Cisco · Cisco Open Source Snort3
- affected 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
- and 65 more
Cisco · Cisco Secure Firewall Threat Defense (FTD) Software
- affected 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
- and 20 more
Cisco · Cisco Umbrella Insights Virtual Appliance
- affected 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
- and 33 more
Cisco · Cisco UTD SNORT IPS Engine Software
- affected 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
- and 76 more
What to do
Exploitation: The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
References (1)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-20221)Record last updated .