There is a workaround that addresses these vulnerabilities. To remove the attack vector for these vulnerabilities for Cisco FMC Software-managed devices and Cisco Defense Orchestrator-managed devices, configure a fastpath prefilter rule to bypass the Snort detection engine. To remove the attack vector for these vulnerabilities for Cisco Firepower Device Manager (FDM)-managed devices, configure an access control rule to bypass the Snort detection engine.
Workaround for Cisco FMC Software-Managed Devices
To configure a fastpath prefilter rule for SMB traffic for Cisco FMC Software-managed devices, do the following:
Log in to the FMC web interface.
From the Policies menu, under the Access Control section, choose Prefilter.
Choose New Policy.
Enter the Name and Description and click Save.
In the resulting window, ensure that Default Action: Tunnel Traffic is set to Analyze all tunnel traffic.
Click Add Prefilter Rule.
In the resulting window, enter a rule Name and ensure the Enabled box is checked.
From the Action drop-down menu, choose Fastpath.
Configure the policy under the Interfaces, Networks, and Vlan Tags tabs for SMB traffic on the affected network.
Click the Port tab.
Enter the following destination ports for SMB traffic: TCP (6):138, TCP (6):139, TCP (6):445 and UDP (17):137.
Click Add to add the policy.
Click Save to save the policy.
To associate the SMB prefilter policy with the access control policy deployed on Cisco FMC Software-managed devices, do the following:
From the Policies menu, under the Access Control section, choose Access Control.
Find the policy of interest.
Click the Edit icon.
Click the name next to Prefilter Policy.
Choose the name of the newly created SMB prefilter policy from the drop-down menu.
Click OK.
For more information, see the Prefiltering and Prefilter Policies ["https://www.cisco.com/c/en/us/td/docs/security/secure-firewall/management-center/device-config/710/management-center-device-config-71/access-prefilter.html"] chapter of the Firepower Management Center Device Configuration Guide.
Workaround for Cisco FDM-Managed Devices
Fastpath is not supported on Cisco FDM-managed devices. Instead, set an access control policy with an action of trust for the appropriate ports.
To configure an access control policy to bypass SMB traffic for Cisco FDM-managed devices, do the following:
Log in to the Cisco FDM web interface.
From the Policies menu, choose Access Control.
Create a new policy by clicking the plus (+) sign.
Enter a name and under the Action drop-down menu, choose Trust.
In the Port section, click the plus (+) sign.
Select Create new Port.
Enter a name, protocol type, and port number for each of the following ports: TCP (6):138, TCP (6):139, TCP (6):445, and UDP (17):137.
Once the ports have been created, select the four ports to be added to the rule by selecting their names.
Click OK when done.
Click OK to add the policy.
Deploy changes to Cisco FTD Software.
For more information, see the Access Control Chapter ["https://www.cisco.com/c/en/us/td/docs/security/firepower/710/fdm/fptd-fdm-config-guide-710/fptd-fdm-access.html"] of the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.
Workaround for Cisco Defense Orchestrator-Managed Devices
To configure a fastpath prefilter rule for SMB traffic for Cisco Defense Orchestrator-managed devices, do the following:
Log in to the Cisco Defense Orchestrator web interface.
From the Policies menu, choose FTD Policies.
From the Policies menu, under the Access Control section, choose Prefilter.
Click New Policy.
Enter the Name and Description and click Save.
In the resulting window, ensure that Default Action: Tunnel Traffic is set to Analyze all tunnel traffic.
Click Add Prefilter Rule.
In the resulting window, enter a rule Name and ensure the Enabled box is checked.
From the Action drop-down menu, select Fastpath.
Configure the policy under the Interfaces, Networks, and Vlan Tags tabs for SMB traffic on the affected network.
Click the Port tab.
Enter the following destination ports for SMB traffic: TCP (6):138, TCP (6):139, TCP (6):445, and UDP (17):137.
Click Add to add the policy.
Click Save to save the policy.
To associate the SMB prefilter policy with the access control policy deployed on Cisco Defense Orchestrator-managed devices, do the following:
From the Policies menu, under the Access Control section, choose Access Control.
Find the policy of interest.
Click the Edit icon.
Click the name next to Prefilter Policy.
Choose the name of the newly created SMB prefilter policy from the drop-down menu.
Click OK.
For more information, see the Cisco Defense Orchestrator website ["https://docs.defenseorchestrator.com/"].
While this workaround has been deployed and was proven successful in a test environment, customers should determine the applicability and effectiveness in their own environment and under their own use conditions. Customers should be aware that any workaround or mitigation that is implemented may negatively impact the functionality or performance of their network based on intrinsic customer deployment scenarios and limitations. Customers should not deploy any workarounds or mitigations before first evaluating the applicability to their own environment and any impact to such environment.