Multiple Cisco Products Snort 3 SMTP MIME Denial of Service Vulnerability

Description

Multiple Cisco products are affected by a vulnerability in the Snort 3 SMTP MIME Decoder that could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart. This vulnerability is due to a lack of error checking when the MIME fields of the SMTP header are parsed. An attacker could exploit this vulnerability by sending crafted SMTP packets through an established connection to be parsed by Snort 3. A successful exploit could allow the attacker to cause a denial of service (DoS) condition when the Snort 3 Detection Engine unexpectedly restarts. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. This advisory is available at the following link: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort3-mime-vulns-bkXjcKkt This advisory is part of a group of advisories. For a complete list of the advisories and links to them, see Cisco Advance Notification for Publication of October 21, 2026, Security Advisories . In addition, for further documentation of improvements and fixes in Snort 3, see Multiple Cisco Products Snort 3 Security Hardening Release: October 2026 . Security Impact Rating: Medium CVE: CVE-2026-20011

What to do

Install the fixed versions listed in the official advisory. If you cannot update right away, apply the workarounds or mitigations it describes and limit access to the affected service.

Details

Vendor

Cisco

Product

Snort 3

CVE

CVE-2026-20011

Affected versions

Cisco Open Source Snort3 3.1: 70 versions, from 3.1.2.0 to 3.1.84.0
Cisco Open Source Snort3 3.2: 3.2.1.0; 3.2.2.0
Cisco Open Source Snort3 3.3: 7 versions, from 3.3.0.0 to 3.3.7.0
Cisco Open Source Snort3 3.5: 3.5.0.0; 3.5.1.0; 3.5.2.0
Cisco Open Source Snort3 3.8: 3.8.1.0
Cisco Open Source Snort3 3.6: 4 versions, from 3.6.0.0 to 3.6.3.0
Cisco Open Source Snort3 3.9: 7 versions, from 3.9.0.0 to 3.9.7.0
Cisco Open Source Snort3 3.7: 5 versions, from 3.7.0.0 to 3.7.4.0
Cisco Open Source Snort3 3.10: 3.10.0.0
Cisco Secure Firewall Threat Defense (FTD) Software 7.0: 17 versions, from 7.0.0 to 7.0.9
Cisco Secure Firewall Threat Defense (FTD) Software 7.2: 18 versions, from 7.2.0 to 7.2.11
Cisco Secure Firewall Threat Defense (FTD) Software 7.3: 4 versions, from 7.3.0 to 7.3.1.2
Cisco Secure Firewall Threat Defense (FTD) Software 7.4: 10 versions, from 7.4.0 to 7.4.4
Cisco Secure Firewall Threat Defense (FTD) Software 7.6: 5 versions, from 7.6.0 to 7.6.4
Cisco Secure Firewall Threat Defense (FTD) Software 7.7: 4 versions, from 7.7.0 to 7.7.11
Cisco Secure Firewall Threat Defense (FTD) Software 10.0: 10.0.0
Cisco UTD SNORT IPS Engine Software 3.17: 3.17.0S; 3.17.1S
Cisco UTD SNORT IPS Engine Software 16.12: 8 versions, from 16.12.1a to 16.12.8
Cisco UTD SNORT IPS Engine Software 16.9: 7 versions, from Fuji-16.9.2 to Fuji-16.9.8
Cisco UTD SNORT IPS Engine Software 17.3: 8 versions, from 17.3.1a to 17.3.8
Cisco UTD SNORT IPS Engine Software 16.6: 9 versions, from Everest-16.6.2 to 16.6.10
Cisco UTD SNORT IPS Engine Software 16.3: 5 versions, from Denali-16.3.3 to Denali-16.3.9
Cisco UTD SNORT IPS Engine Software 17.2: 17.2.1r
Cisco UTD SNORT IPS Engine Software 17.1: 17.1.1
Cisco UTD SNORT IPS Engine Software 17.4: 17.4.1a; 17.4.1b; 17.4.2
Cisco UTD SNORT IPS Engine Software 17.5: 17.5.1a
Cisco UTD SNORT IPS Engine Software 17.6: 8 versions, from 17.6.1a to 17.6.8a
Cisco UTD SNORT IPS Engine Software 17.7: 17.7.1a; 17.7.2
Cisco UTD SNORT IPS Engine Software 17.8: 17.8.1a
Cisco UTD SNORT IPS Engine Software 17.9: 12 versions, from 17.9.1a to 17.9.9 (from the advisory and NVD; check the exact builds in the official advisory)

CVSS score

5.8

Actively exploited

Not known at this time

Source

Cisco PSIRT – original advisory

Published

October 22, 2026

The description and the recommended action are quoted from the public advisory (the action is our generic advice); severity, exploitation status and affected versions are compiled automatically from public sources and may contain errors. The vendor's original advisory prevails: check it before taking action. This information is provided without warranty and does not replace a professional assessment.