Summary

• A vulnerability in the memory management handling for the Snort 3 Detection Engine of Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart.

  This vulnerability is due to a logic error in memory management when a device is performing Snort 3 SSL packet inspection. An attacker could exploit this vulnerability by sending crafted SSL packets through an established connection to be parsed by the Snort 3 Detection Engine. 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-ftd-snort3ssl-FBEKYXpH

  This advisory is part of the March 2026 release of the Cisco Secure Firewall ASA, Secure FMC, and Secure FTD Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: March 2026 Semiannual Cisco Secure Firewall ASA, Secure FMC, and Secure FTD Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  At the time of publication, this vulnerability affected Cisco devices if they were running a vulnerable release of Cisco Secure FTD Software and the following conditions were met:

  • Snort 3 was enabled.
  • An SSL policy was configured.

  For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.

  Determine the Snort Configuration on Cisco Secure FTD Software

  To determine if Snort 3 is running on Cisco Secure FTD Software, see Determine the Active Snort Version that Runs on Firepower Threat Defense (FTD). Snort 3 has to be active for this vulnerability to be exploited.

  Determine Cisco Secure FTD Software SSL Policy Configuration

  SSL decryption policies are not configured by default.

  Determine Cisco Secure FTD Software SSL Policy Configuration Using the CLI

  To determine whether an SSL policy is configured on a device that is running Cisco Secure FTD Software, log in to the Cisco Secure FTD Software CLI and use the show ssl-policy-config command. If the command output shows a policy, the device has an SSL policy applied and is affected by this vulnerability, as shown in the following example:

  > show ssl-policy-config
  =================[ Default Action ]=================
  Default Action            : Do Not Decrypt
  ...

  In the following example, no SSL policy is applied:

  >show ssl-policy-config
  SSL policy not yet applied

  Determine Cisco Secure FTD Software SSL Policy Configuration for Devices Managed by Cisco Secure FDM Software

  To determine whether an SSL policy is configured on a device that is managed by Cisco Secure Firepower Device Manager (FDM) Software, complete the following steps:

  1. Log in to the Cisco Secure FTD web interface.
  2. From the main menu, choose Policies.
  3. Choose the SSL Decryption tab.
  • If a Policy Name is listed, the device is affected by this vulnerability.
  • If SSL decryption is not enabled, the device is not affected by this vulnerability.

  For detailed information about SSL decryption policies, see the SSL Decryption chapter of the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

  Determine Cisco Secure FTD Software SSL Policy Configuration for Devices Managed by Cisco Secure FMC Software

  To determine whether an SSL policy is configured on a device that is managed by Cisco Secure Firewall Management Center (FMC) Software, complete the following steps:

  1. Log in to the Cisco Secure FMC web interface.
  2. From the Policies menu, choose Access Control.
  3. Choose the appropriate access control policy.
  4. Click the Edit pencil icon.
  5. Look in the SSL Policy area.
     
     • If a Policy Name is listed, the device is affected by this vulnerability.
     • If None is listed, the device is not affected by this vulnerability.

  For detailed information about SSL decryption policies, see the SSL Policies chapter of the Cisco Secure Firewall Management Center Device Configuration Guide.

  Determine Cisco FTD Software SSL Policy Configuration for Devices Managed by Cisco Defense Orchestrator

  To determine whether an SSL policy is configured on a device that is managed by Cisco Defense Orchestrator, complete the following steps:

  1. Log in to the Cisco Defense Orchestrator web interface.
  2. From the Policies menu, choose FTD Policies.
  3. From the FTD Policies menu, choose Access Control.
  4. Choose the appropriate access control policy.
  5. Click the Edit pencil icon.
  6. Look in the Decryption Policy area.
  • If a Policy Name is listed, the device is affected by this vulnerability.
  • If None is listed, the device is not affected by this vulnerability.

  For detailed information about devices that are managed by Cisco Defense Orchestrator, see the Cisco Defense Orchestrator documentation.

  Products Confirmed Not Vulnerable

  Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.

  Cisco has confirmed that this vulnerability does not affect the following products:

  • Cisco Cyber Vision Software
  • Cisco Meraki products
  • Cisco Secure Access - Secure Internet Access (SIA) Advantage
  • Cisco Secure Access - Secure Private Access (SPA) Advantage
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
  • Cisco Secure FMC Software
  • Cisco Secure FTD Software with Snort 2 configured
  • Cisco Umbrella Cloud-delivered Firewall (CDFW), formerly Umbrella Secure Internet Gateway (SIG)
  • Cisco Unified Threat Defense (UTD) Software
  • Open Source Snort 2 Software
  • Open Source Snort 3 Software

Workarounds

• There are no workarounds that address this vulnerability.

Fixed Software

• Cisco considers any workarounds and mitigations (if applicable) to be temporary solutions until an upgrade to a fixed software release is available. To fully 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.

  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.

  Only this advisoryAll Critical and High advisoriesAll advisoriesCisco ASA SoftwareCisco FMC SoftwareCisco FTD SoftwareAny Platform3000 Series Industrial Security Appliances (ISA)ASA 5500-X Series FirewallsASA Service ModuleAdaptive Security Virtual Appliance (ASAv)Firepower 1000 SeriesFirepower 2100 SeriesFirepower 4100 SeriesFirepower 9000 SeriesSecure Firewall 1200 SeriesSecure Firewall 3100 SeriesSecure Firewall 4200 Series

   

  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

Exploitation and Public Announcements

• The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.

Source

• This vulnerability was found during the resolution of a Cisco Technical Assistance Center (TAC) support case.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-snort3ssl-FBEKYXpH

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	—	Final	2026-MAR-04

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