CVE-2026-20066: Multiple Cisco Products Snort 3 TBD Denial of Service Vulnerability
Published Mar 4, 2026
·Updated
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.
Affected Software
89 affected components
Cisco Snort 3
Cisco Snort>=3.0.0-233<3.9.7.0
Cisco Secure Firewall Threat Defense=7.4.0
Cisco Secure Firewall Threat Defense=7.4.1
Cisco Secure Firewall Threat Defense=7.4.1.1
Cisco Secure Firewall Threat Defense=7.4.2
Cisco Secure Firewall Threat Defense=7.4.2.1
Cisco Secure Firewall Threat Defense=7.4.2.2
Cisco Secure Firewall Threat Defense=7.4.2.3
Cisco Secure Firewall Threat Defense=7.4.2.4
Cisco Secure Firewall Threat Defense=7.4.3
Cisco Secure Firewall Threat Defense=7.6.0
Cisco Secure Firewall Threat Defense=7.6.1
Cisco Secure Firewall Threat Defense=7.6.2
Cisco Secure Firewall Threat Defense=7.6.2.1
Cisco Secure Firewall Threat Defense=7.7.0
Cisco Secure Firewall Threat Defense=7.7.10
Cisco Secure Firewall Threat Defense=7.7.10.1
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.2.1r
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.3.1a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.3.2
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.3.3
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.3.4
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.3.4a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.3.5
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.3.6
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.3.7
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.3.8
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.3.8a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.4.1a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.4.1b
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.4.2
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.5.1
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.5.1a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.6.1a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.6.2
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.6.3
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.6.3a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.6.4
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.6.5
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.6.6
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.6.6a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.6.7
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.6.8
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.6.8a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.7.1a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.7.2
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.8.1a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.9.1a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.9.2a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.9.3a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.9.4
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.9.4a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.9.5a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.9.5e
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.9.5f
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.9.6
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.9.7a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.9.7b
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.9.8
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.10.1a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.11.1a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.12.1a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.12.2
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.12.3
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.12.3a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.12.4
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.12.4a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.12.4b
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.12.5
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.12.5a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.12.5b
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.12.5c
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.12.5d
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.12.6
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.13.1a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.14.1a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.15.1a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.15.2a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.15.2c
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.15.3
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.15.3a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.15.4
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.15.4c
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.16.1a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.17.1
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.18.1
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.18.1a
Cisco Unified Threat Defense Snort Intrusion Prevention System Engine=17.18.2
Event History
Mar 4, 2026
CVE Published
via MITRE·05:49 PM
Data Sourced
via MITRE·05:49 PM
DescriptionSeverityWeakness
Data Sourced
via NVD·06:16 PM
DescriptionSeverityWeaknessAffected Software
Frequently Asked Questions
1
What is the severity of CVE-2026-20066?
CVE-2026-20066 is classified as a high-severity vulnerability due to its potential to cause a denial of service.
2
How do I fix CVE-2026-20066?
To mitigate CVE-2026-20066, ensure that you are running the latest version of Cisco Snort 3 that includes the necessary patches.
3
What type of attack can exploit CVE-2026-20066?
CVE-2026-20066 can be exploited by an unauthenticated, remote attacker to restart the Snort 3 Detection Engine.
4
Which Cisco products are affected by CVE-2026-20066?
CVE-2026-20066 affects multiple Cisco products that utilize the Snort 3 Detection Engine.
5
What are the potential impacts of CVE-2026-20066?
Exploiting CVE-2026-20066 could result in intermittent service interruptions and downtime for network packet processing.