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: 2026-10-22

Assigner: Cisco Systems, Inc.

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

Published
2026-10-21
Last Modified
2026-10-22
Generated
2026-11-10
AI Q&A
2026-10-22
EPSS Evaluated
2026-11-09
NVD
EUVD

Affected Vendors & Products

Showing 203 associated CPEs
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
CWE Icon
KEV
KEV Icon
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.

Attack-Flow Graph

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Executive Summary

This vulnerability affects multiple Cisco products using the Snort 3 Teredo Detection Engine. It occurs due to incomplete error checking when parsing Teredo packets. An attacker can exploit it by sending a crafted Teredo packet to trigger a restart of the Snort 3 Detection Engine, causing a denial-of-service condition and interrupting packet inspection.

Impact Analysis

The vulnerability can lead to a denial-of-service condition, disrupting network traffic inspection and potentially causing service interruptions. It may affect network security monitoring and expose systems to further attacks if packet inspection is halted.

Mitigation Strategies

Apply the latest Cisco Snort 3 software update or patch to address the incomplete error checking in the Teredo Detection Engine. Monitor network traffic for unusual Teredo packet patterns that may indicate exploitation attempts.

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