CVE-2026-20197
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Denial of Service in Cisco Snort 3 Teredo Detection Engine
Vulnerability report for CVE-2026-20197, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-10-21
Last updated on: 2026-10-21
Assigner: Cisco Systems, Inc.
Description
Description
Multiple Cisco products are affected by a vulnerability in the Snort 3 Teredo Detection Engine that could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart, resulting in an interruption of packet inspection.
This vulnerability is due to incomplete error checking when Snort 3 parses Teredo packets. An attacker could exploit this vulnerability by sending a crafted Teredo packet to a targeted device to be parsed by Snort. A successful exploit could allow the attacker to cause the Snort 3 Detection Engine to restart unexpectedly, resulting in a DoS condition.
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| Cisco | Cisco | Open Source Snort3 3.12.2.0 |
| Cisco | Cisco | Open Source Snort3 3.1.2.0 |
| Cisco | Cisco | Open Source Snort3 3.1.3.0 |
| Cisco | Cisco | Open Source Snort3 3.1.4.0 |
| Cisco | Cisco | Open Source Snort3 3.1.5.0 |
| Cisco | Cisco | Open Source Snort3 3.1.6.0 |
| Cisco | Cisco | Open Source Snort3 3.1.7.0 |
| Cisco | Cisco | Open Source Snort3 3.1.8.0 |
| Cisco | Cisco | Open Source Snort3 3.1.9.0 |
| Cisco | Cisco | Open Source Snort3 3.1.10.0 |
| Cisco | Cisco | Open Source Snort3 3.1.12.0 |
| Cisco | Cisco | Open Source Snort3 3.1.13.0 |
| Cisco | Cisco | Open Source Snort3 3.1.14.0 |
| Cisco | Cisco | Open Source Snort3 3.1.15.0 |
| Cisco | Cisco | Open Source Snort3 3.1.16.0 |
| Cisco | Cisco | Open Source Snort3 3.1.17.0 |
| Cisco | Cisco | Open Source Snort3 3.1.18.0 |
| Cisco | Cisco | Open Source Snort3 3.1.19.0 |
| Cisco | Cisco | Open Source Snort3 3.1.20.0 |
| Cisco | Cisco | Open Source Snort3 3.1.21.0 |
| Cisco | Cisco | Open Source Snort3 3.1.22.0 |
| Cisco | Cisco | Open Source Snort3 3.1.23.0 |
| Cisco | Cisco | Open Source Snort3 3.1.24.0 |
| Cisco | Cisco | Open Source Snort3 3.1.25.0 |
| Cisco | Cisco | Open Source Snort3 3.1.27.0 |
| Cisco | Cisco | Open Source Snort3 3.1.28.0 |
| Cisco | Cisco | Open Source Snort3 3.1.29.0 |
| Cisco | Cisco | Open Source Snort3 3.1.30.0 |
| Cisco | Cisco | Open Source Snort3 3.1.31.0 |
| Cisco | Cisco | Open Source Snort3 3.1.32.0 |
| Cisco | Cisco | Open Source Snort3 3.1.36.0 |
| Cisco | Cisco | Open Source Snort3 3.1.38.0 |
| Cisco | Cisco | Open Source Snort3 3.1.39.0 |
| Cisco | Cisco | Open Source Snort3 3.1.40.0 |
| Cisco | Cisco | Open Source Snort3 3.1.41.0 |
| Cisco | Cisco | Open Source Snort3 3.1.42.0 |
| Cisco | Cisco | Open Source Snort3 3.1.43.0 |
| Cisco | Cisco | Open Source Snort3 3.1.45.0 |
| Cisco | Cisco | Open Source Snort3 3.1.47.0 |
| Cisco | Cisco | Open Source Snort3 3.1.48.0 |
| Cisco | Cisco | Open Source Snort3 3.1.50.0 |
| Cisco | Cisco | Open Source Snort3 3.1.51.0 |
| Cisco | Cisco | Open Source Snort3 3.1.52.0 |
| Cisco | Cisco | Open Source Snort3 3.1.53.0 |
| Cisco | Cisco | Open Source Snort3 3.1.55.0 |
| Cisco | Cisco | Open Source Snort3 3.1.56.0 |
| Cisco | Cisco | Open Source Snort3 3.1.57.0 |
| Cisco | Cisco | Open Source Snort3 3.1.58.0 |
| Cisco | Cisco | Open Source Snort3 3.1.59.0 |
| Cisco | Cisco | Open Source Snort3 3.1.60.0 |
| Cisco | Cisco | Open Source Snort3 3.1.61.0 |
| Cisco | Cisco | Open Source Snort3 3.1.62.0 |
| Cisco | Cisco | Open Source Snort3 3.1.63.0 |
| Cisco | Cisco | Open Source Snort3 3.1.64.0 |
| Cisco | Cisco | Open Source Snort3 3.1.65.0 |
| Cisco | Cisco | Open Source Snort3 3.1.66.0 |
| Cisco | Cisco | Open Source Snort3 3.1.67.0 |
| Cisco | Cisco | Open Source Snort3 3.1.69.0 |
| Cisco | Cisco | Open Source Snort3 3.1.70.0 |
| Cisco | Cisco | Open Source Snort3 3.1.71.0 |
| Cisco | Cisco | Open Source Snort3 3.1.72.0 |
| Cisco | Cisco | Open Source Snort3 3.1.73.0 |
| Cisco | Cisco | Open Source Snort3 3.1.74.0 |
| Cisco | Cisco | Open Source Snort3 3.1.75.0 |
| Cisco | Cisco | Open Source Snort3 3.1.76.0 |
| Cisco | Cisco | Open Source Snort3 3.1.77.0 |
| Cisco | Cisco | Open Source Snort3 3.1.78.0 |
| Cisco | Cisco | Open Source Snort3 3.1.81.0 |
| Cisco | Cisco | Open Source Snort3 3.1.82.0 |
| Cisco | Cisco | Open Source Snort3 3.1.83.0 |
| Cisco | Cisco | Open Source Snort3 3.1.84.0 |
| Cisco | Cisco | Open Source Snort3 3.2.1.0 |
| Cisco | Cisco | Open Source Snort3 3.2.2.0 |
| Cisco | Cisco | Open Source Snort3 3.3.0.0 |
| Cisco | Cisco | Open Source Snort3 3.3.1.0 |
| Cisco | Cisco | Open Source Snort3 3.3.2.0 |
| Cisco | Cisco | Open Source Snort3 3.3.3.0 |
| Cisco | Cisco | Open Source Snort3 3.3.4.0 |
| Cisco | Cisco | Open Source Snort3 3.3.5.0 |
| Cisco | Cisco | Open Source Snort3 3.3.7.0 |
| Cisco | Cisco | Open Source Snort3 3.5.0.0 |
| Cisco | Cisco | Open Source Snort3 3.5.1.0 |
| Cisco | Cisco | Open Source Snort3 3.8.1.0 |
| Cisco | Cisco | Open Source Snort3 3.6.0.0 |
| Cisco | Cisco | Open Source Snort3 3.6.2.0 |
| Cisco | Cisco | Open Source Snort3 3.9.3.0 |
| Cisco | Cisco | Open Source Snort3 3.7.2.0 |
| Cisco | Cisco | Open Source Snort3 3.7.0.0 |
| Cisco | Cisco | Open Source Snort3 3.9.6.0 |
| Cisco | Cisco | Open Source Snort3 3.10.0.0 |
| Cisco | Cisco | Open Source Snort3 3.10.2.0 |
| Cisco | Cisco | Open Source Snort3 3.7.4.0 |
| Cisco | Cisco | Open Source Snort3 3.9.0.0 |
| Cisco | Cisco | Open Source Snort3 3.5.2.0 |
| Cisco | Cisco | Open Source Snort3 3.12.1.0 |
| Cisco | Cisco | Open Source Snort3 3.6.1.0 |
| Cisco | Cisco | Open Source Snort3 3.9.2.0 |
| Cisco | Cisco | Open Source Snort3 3.6.3.0 |
| Cisco | Cisco | Open Source Snort3 3.9.5.0 |
| Cisco | Cisco | Open Source Snort3 3.7.1.0 |
| Cisco | Cisco | Open Source Snort3 3.9.7.0 |
| Cisco | Cisco | Open Source Snort3 3.7.3.0 |
| Cisco | Cisco | Open Source Snort3 3.10.1.0 |
| Cisco | Cisco | Open Source Snort3 3.9.1.0 |
| Cisco | Cisco | Open Source Snort3 3.11.1.0 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.0 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.0.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.1.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.2 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.0 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.2.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.3 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.0.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.4 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.5 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.3.0 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.2 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.3 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.3.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.4 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.6 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.5 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.4.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.3.1.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.0 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.6.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.5.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.6 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.6.2 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.1.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.7 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.5.2 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.3.1.2 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.8 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.6.0 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.2 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.8.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.6.3 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.2.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.9 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.7 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.7.0 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.2.2 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.10 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.6.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.2.3 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.8 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.6.2 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.7.10 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.7.11 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.8.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.6.2.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.7.10.1 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.2.4 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.10.2 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.3 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.6.4 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 10.0.0 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.4 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.0.9 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.2.11 |
| Cisco | Cisco | Secure Firewall Threat Defense (FTD) Software 7.4.7 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.1a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.2 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.13.1a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.3 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.14.1a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.4 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.3a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.1a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.16.1a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.4a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.2c |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.4b |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.2a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.5 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.17.1 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.5a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.3a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.3 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.5b |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.5c |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.4 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.18.1 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.18.1a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.6 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.4c |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.5d |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.18.2 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 26.1.1 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.5 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.5a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.7 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.7a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.7b |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.18.3a |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.12.8 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.15.6 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 17.18.4 |
| Cisco | Cisco | UTD SNORT IPS Engine Software 26.1.2 |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-119 | The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data. |
