Secure Firewall ASA and FTD
CVE-2026-20066: Multiple Cisco Products Snort 3 TBD Denial of Service Vulnerability
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.
Published
ExploitedNot in CISA KEV
Ransomware useNot reportedPer CISA
SeverityMEDIUMCVSS 3.1 5.8
EPSS0.47%Chance of exploitation in 30 days
Public exploitNot tracked
FixNot yet
Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.
Affected and fixed versions
| Product / branch | Fixed in |
|---|---|
| Cisco Secure Firewall Threat Defense (FTD) Software 7.4 | See the advisory |
| Cisco Secure Firewall Threat Defense (FTD) Software 7.4 | See the advisory |
| Cisco Secure Firewall Threat Defense (FTD) Software 7.4 | See the advisory |
| Cisco Secure Firewall Threat Defense (FTD) Software 7.6 | See the advisory |
| Cisco Secure Firewall Threat Defense (FTD) Software 7.4 | See the advisory |
| Cisco Secure Firewall Threat Defense (FTD) Software 7.4 | See the advisory |
| Cisco Secure Firewall Threat Defense (FTD) Software 7.7 | See the advisory |
| Cisco Secure Firewall Threat Defense (FTD) Software 7.4 | See the advisory |
| Cisco Secure Firewall Threat Defense (FTD) Software 7.6 | See the advisory |
| Cisco Secure Firewall Threat Defense (FTD) Software 7.4 | See the advisory |
| Cisco Secure Firewall Threat Defense (FTD) Software 7.6 | See the advisory |
| Cisco Secure Firewall Threat Defense (FTD) Software 7.7 | See the advisory |
| Cisco Secure Firewall Threat Defense (FTD) Software 7.6 | See the advisory |
| Cisco Secure Firewall Threat Defense (FTD) Software 7.7 | See the advisory |
| Cisco Secure Firewall Threat Defense (FTD) Software 7.4 | See the advisory |
| Cisco Secure Firewall Threat Defense (FTD) Software 7.4 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.3 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.2 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.3 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.4 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.5 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.3 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.5 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.3 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.3 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.4 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.4 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.6 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.7 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.6 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.8 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.3 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.6 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.6 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.7 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.9 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.6 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.10 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.3 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.3 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.9 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.6 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.11 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.9 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.12 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.9 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.6 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.3 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.3 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.6 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.9 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.12 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.13 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.9 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.12 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.6 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.14 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.12 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.12 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.15 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.6 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.9 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.6 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.16 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.9 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.12 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.15 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.9 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.12 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.15 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.12 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.17 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.12 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.9 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.15 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.15 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.12 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.12 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.15 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.9 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.18 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.18 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.12 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.9 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.15 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.12 | See the advisory |
| Cisco UTD SNORT IPS Engine Software 17.18 | See the advisory |
Always confirm against the vendor advisory, which lists every fixed hotfix.
What it is
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.
Exploitation
The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerabilities that are described in this advisory.
Sources
KEV status, EPSS score and vendor data refreshed automatically, last on 11 Oct 2026.