Multiple Cisco Products Snort 3 SMTP MIME Denial of Service Vulnerability

There are no workarounds that address this vulnerability.

Cisco considers any workarounds and mitigations (if applicable) to be temporary solutions until an upgrade to a fixed software release is available. To remediate this vulnerability and avoid future exposure as described in this advisory, Cisco strongly recommends that customers upgrade to the fixed software indicated in this advisory.

Fixed Releases

The Cisco Product Security Incident Response Team (PSIRT) validates only the affected and fixed release information that is documented in this advisory.

For information about fixed releases, see the following sections.

Open Source Snort 3

At the time of publication, the release information in the following table was accurate.

The left column lists Snort 3 software releases, and the right column indicates whether a release was affected by the vulnerability that is described in this advisory and which release included the fix for this vulnerability.

*This fix is also included as part of the broader hardening improvements that are disclosed in the security advisory Multiple Cisco Products Snort 3 Security Hardening Release: October 2026.

Cisco Secure Firewall ASA, Secure FMC, and Secure FTD Software

To help customers determine their exposure to vulnerabilities in Cisco Secure Firewall ASA, Secure FMC, and Secure FTD Software, Cisco provides the Cisco Software Checker. This tool identifies any Cisco security advisories that impact a specific software release and the earliest release that fixes the vulnerabilities that are described in each advisory (“First Fixed”).

If applicable, the tool also returns the earliest release that fixes all the vulnerabilities that are described in all the advisories that the Software Checker identifies (“Combined First Fixed”).

To use the tool, go to the Cisco Software Checker page and follow the instructions. Alternatively, use the following form to search for vulnerabilities that affect a specific software release. To use the form, follow these steps:

1. Choose which advisories the tool will search-all advisories, only advisories with a Critical or High Security Impact Rating (SIR), or only this advisory.

2. Choose the appropriate software.

3. Choose the appropriate platform.

4. Enter a release number-for example, 9.20.3.4 for Cisco Secure Firewall ASA Software or 7.4.2 for Cisco Secure FTD Software.

5. Click Check.

For instructions on upgrading a Cisco Secure FTD device, see the appropriate Cisco Secure FMC upgrade guide.

Additional Resources

For help determining the best Cisco Secure FTD Software release, see the following Recommended Releases documents. If a security advisory recommends a later release, Cisco recommends following the advisory guidance.

Cisco Secure Firewall Threat Defense Compatibility Guide

UTD on Cisco IOS XE Software: CSCwt04581

At the time of publication, the release information in the following table was accurate. See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information.

In the following table, the left column lists Cisco IOS XE Software releases, and the right column indicates whether a release was affected by the vulnerability that is described in this advisory and which release included the fix for this vulnerability.

Cisco Meraki MX Security Appliances

Snort is integrated natively into Cisco Meraki security appliances as part of the threat protection services that are managed automatically through the Meraki Dashboard. No customer action is required to download Meraki firmware or the Snort 3 package for Meraki devices. As of October 21, 2026, all Meraki models listed in this advisory that are online and connected to the Cisco Meraki Dashboard have been automatically updated with the Snort 3 package.