Vulnslist

There is a workaround and mitigations that address this vulnerability. To remove the attack vector for this vulnerability, do one of the following:

Revert to Snort 2.
Remain on Snort 3 but ensure that neither of the following is configured:
An SSL policy with a URL category configured.
An Access Control policy with TLS Server Identity Discovery enabled and a URL category configured.

Note: A Decryption policy or SSL policy does not need to be configured and associated with the Access Control policy for TLS Server Identity Discovery to be enabled.
Revert to Snort 2
Before downgrading, review the Before you Begin section in the Switching Between Snort 2 and Snort 3 https://www.cisco.com/c/en/us/td/docs/security/firepower/730/fdm/fptd-fdm-config-guide-730/fptd-fdm-intrusion.html?bookSearch=true#id_120089 section of the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

Note: Downgrading to Snort 2 will delete customer policies, NAP customizations, and Hostname redirect in active authentications. To discuss the effects of reverting on the deployment, contact the Technical Assistance Center (TAC) https://www.cisco.com/go/tac/

Revert to Snort 2 for Cisco FTD devices by using the CLI

There is no option to change this configuration by using the CLI.

Revert to Snort 2 for Cisco FTD devices that are managed by FDM Software

To revert to Snort 2 on a device that is managed by Cisco FDM Software, complete the following steps:

Log in to the Cisco FTD Software web interface.
From the main menu, choose Device.
In the Updates area, choose View Configuration.
In the Intrusion Rule section, choose Downgrade to 2.0.

After making the changes above, deploy changes to your Cisco FTD devices.

For detailed information about reverting to Snort 2, see the Switching Between Snort 2 and Snort 3 https://www.cisco.com/c/en/us/td/docs/security/firepower/730/fdm/fptd-fdm-config-guide-730/fptd-fdm-intrusion.html?bookSearch=true#id_120089 section of the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

Revert to Snort 2 for Cisco FTD devices that are managed by FMC Software

To revert to Snort 2 on a device that is managed by Cisco FMC Software, complete the following steps:

Log in to the Cisco FMC Software web interface.
From the Devices menu, choose Device Management.
Choose the appropriate Cisco FTD device.
Click the Edit pencil icon.
Choose the Device tab.
In the Inspection Engine area, choose Revert to Snort 2.

After making the changes above, deploy changes to your Cisco FTD devices.

For detailed information about reverting to Snort 2, see the Snort 3 Inspection Engine https://www.cisco.com/c/en/us/td/docs/security/secure-firewall/management-center/snort/720/snort3-configuration-guide-v72/migrating.html#concept_D87B73A83ACA42CCA656F0041F9D860B-enabledisable chapter of the Cisco Secure Firewall Management Center Snort 3 Configuration Guide.

Revert to Snort 2 for Cisco FTD devices managed by Cisco Defense Orchestrator

To revert to Snort 2 on a device that is managed by Cisco Defense Orchestrator, complete the following steps:

Log in to the Cisco Defense Orchestrator web interface.
In the navigation bar, click Inventory.
Click the Devices tab.
Click the FTD tab and click the device you want to revert.
In the Device Actions pane located to the right, click Upgrade.
Set the upgrade toggle to Intrusion Prevention Engine.
Click Revert to Snort Engine 2.0.

After making the changes above, deploy changes to your Cisco FTD devices.

For detailed information about Cisco Defense Orchestrator managed devices, see the Cisco Defense Orchestrator documentation. https://docs.defenseorchestrator.com/#!g-managing-security-and-network-devices-with-cdo.html

For detailed information about reverting to Snort 2 for Cisco FMC Devices managed by Cisco Defense Orchestrator, see the Snort 3 Inspection Engine https://www.cisco.com/c/en/us/td/docs/security/secure-firewall/management-center/snort/720/snort3-configuration-guide-v72/migrating.html#concept_D87B73A83ACA42CCA656F0041F9D860B-enabledisable chapter of the Cisco Secure Firewall Management Center Snort 3 Configuration Guide.

For detailed information about reverting to Snort 2 for Cisco FDM Devices managed with Cisco Defense Orchestrator, see the Revert From Snort 3.0 for FDM-Managed Device https://www.cisco.com/c/en/us/td/docs/security/cdo/managing-ftd-with-cdo/managing-ftd-with-cisco-defense-orchestrator/onboard-devices-and-services.html?bookSearch=true#Revert_From_Snort_3_for_FTD section of Managing FDM Devices with Cisco Defense Orchestrator.
Mitigations for Cisco FDM Managed Devices
For Cisco FTD devices that stay on Snort 3, both the access control policy and SSL policy must be checked to ensure the device is not affected by this vulnerability. If either place is configured in a vulnerable manner, the device is affected by this vulnerability.

Access Control Policy

If the device is using an access control policy with TLS server identity discovery enabled and URL categories configured, the device is affected by this vulnerability. The following options can be used to close the vector of attack:

Disable the TLS server identity discovery and leave the URL categories configured.
Remove the URL categories configuration and leave the TLS server identity enabled.

SSL Policy

If the device is using an SSL policy with URL categories configured, the device is affected by this vulnerability. The following options can be used to close the vector of attack:

Remove the URL categories configuration from the SSL policy.
Remove the SSL policy from the access control policy.
Disable TLS Server Identity Discovery
Disabling TLS Server Identity Discovery Cisco FTD devices using the CLI

There is no option to change this configuration using the CLI.

Disabling TLS Server Identity Discovery Cisco for Devices that are Managed by Cisco FDM Software

To disable the TLS server identity discovery for Cisco FDM Software-managed devices, do the following:

Log in to the Cisco FDM web interface.
From the Policies menu, choose Access Control.
Click the Settings gear icon.
If the TLS Server Identity Discovery setting is enabled, disable it and click OK.

After changing the policies above, deploy the new policies to your Cisco FTD devices.

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.

Disabling TLS Server Identity Discovery Cisco for Devices that are Managed by Cisco FMC Software

To disable the TLS server identity discovery for devices that are managed by Cisco FMC Software, do the following:

Log in to the Cisco FMC web interface.
From the Policies menu, choose Access Control.
Choose the appropriate Access Control Policy.
Click the Edit pencil icon.
Click on the Advanced tab.
Locate the TLS Server Identity Discovery setting.
If the setting is enabled, click the Edit pencil icon.
Uncheck the Early application detection and URL categorization box and choose OK.
Click Save to save the policy.

After changing the policies above, deploy the new policies to your Cisco FTD devices.

For more information, see the Access Control Chapter 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 of the Firepower Management Center Device Configuration Guide.

Disabling TLS Server Identity Discovery Cisco for Devices that are Managed by Cisco Defense Orchestrator

To disable the TLS server identity discovery for devices managed by Cisco Defense Orchestrator, do the following:

Log in to the Cisco Defense Orchestrator web interface.
From the CDO Policies menu, choose FTD Policies.
From the FTD Policies menu, choose Access Control.
Choose the appropriate Access Control Policy.
Click the Edit pencil icon.
Choose More and then click on then Advanced Settings
Locate the TLS Server Identity Discovery setting.
If the setting is enabled, click the Edit pencil icon.
Uncheck the Early application detection and URL categorization box and choose OK.
Click Save to save the policy

After changing the policies above, deploy the new policies to your Cisco Defense Orchestrator devices.

For more information, see the Cisco Defense Orchestrator documentation https://docs.defenseorchestrator.com/ .

For detailed information about TLS server identity discovery for Cisco FMC Devices managed with Cisco Defense Orchestrator, see the Access Control Policies https://www.cisco.com/c/en/us/td/docs/security/cdo/cloud-delivered-firewall-management-center-in-cdo/managing-firewall-threat-defense-services-with-cisco-defense-orchestrator/m_access-policies.html#ID-2176-00000314 chapter of Managing Firewall Threat Defense with Cloud-delivered Firewall Management Center in Cisco Defense Orchestrator.

For detailed information about TLS server identity discovery for Cisco FDM Devices managed with Cisco Defense Orchestrator, see the Configuring FDM-Managed Devices https://www.cisco.com/c/en/us/td/docs/security/cdo/managing-ftd-with-cdo/managing-ftd-with-cisco-defense-orchestrator/configuring-ftd-devices.html?bookSearch=true section of Managing FDM Devices with Cisco Defense Orchestrator.
Removing Access Control Policy URL categories
Removing Access Control Policy URL categories for Cisco FTD devices using the CLI

There is no option to change this configuration using the CLI.

Removing Access Control Policy URL categories for Cisco FTD devices managed by FDM Software

To disable the Access Control Policy URL Category on a device that is managed by Cisco FDM Software, complete the following steps:

Log in to the Cisco FDM web interface.
From the main menu, choose Policies.
Choose the Access Control tab.
For each rule configured, look in the URLs column.
If there is a category listed, then click on the name of the category.
In the pop-up window, click the X next to the name to remove the category and choose OK.

After changing the policies above, deploy the new policies to your Cisco FTD devices.

For detailed information about access control policy URL Categories, see the Access Control https://www.cisco.com/c/en/us/td/docs/security/firepower/730/fdm/fptd-fdm-config-guide-730/fptd-fdm-access.html chapter in the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

Removing Access Control Policy URL categories for Cisco FTD devices managed by FMC Software

To disable the access control policy URL category on a device that is managed by Cisco FMC Software, complete the following steps:

Log in to the Cisco FMC Software web interface.
From the Policies menu, choose Access Control.
Choose the appropriate Access Control Policy.
Click the Edit pencil icon.
For each rule configured, look in the URLs column.
If there is a category listed, then click on the name of the category.
In the pop-up window, click the trash can icon to delete the URL category and choose Save.
Choose Save.

After changing the policies above, deploy the new policies to your FTD devices.

For detailed information about access control policy URL categories, see the Access Control https://www.cisco.com/c/en/us/td/docs/security/firepower/720/fdm/fptd-fdm-config-guide-720/fptd-fdm-access.html?bookSearch=true#topic_96A0CC92335B4F2CB60FAB309DF8EB64 chapter in Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

Removing Access Control Policy URL categories for Cisco FTD devices managed by Cisco Defense Orchestrator

To disable the Access Control Policy URL Category on a device that is managed by Cisco Defense Orchestrator, complete the following steps:

Log in to the Cisco Defense Orchestrator web interface.
From the Cisco Defense Orchestrator Policies menu, choose FTD Policies.
From the FTD Policies menu, choose Access Control.
Choose the appropriate Access Control Policy.
Click the Edit pencil icon.
For each rule configured, look in the URLs column.
If there is a category listed, then click on the name of the category.
In the pop-up window, click the X next to the name to remove the category and choose Apply.
Choose Save.

After changing the policies above, deploy the new policies to your Cisco FTD devices.

For detailed information about Cisco Defense Orchestrator managed devices, see the Cisco Defense Orchestrator documentation. https://docs.defenseorchestrator.com/#!g-managing-security-and-network-devices-with-cdo.html

For detailed information about access control policy URL categories, see the Access Control https://www.cisco.com/c/en/us/td/docs/security/cdo/cloud-delivered-firewall-management-center-in-cdo/managing-firewall-threat-defense-services-with-cisco-defense-orchestrator/m_access-overview.html chapter of Managing Firewall Threat Defense with Cloud-Delivered Firewall Management Center in Cisco Defense Orchestrator.

For detailed information about access control policy URL categories, see the Access Control https://www.cisco.com/c/en/us/td/docs/security/cdo/managing-ftd-with-cdo/managing-ftd-with-cisco-defense-orchestrator/configuring-ftd-devices.html?bookSearch=true#FTD_Access_Control_Policy section of Managing FDM Devices with Cisco Defense Orchestrator guide.
Removing SSL Policy URL categories
Removing SSL Policy URL categories for Cisco FTD devices using the CLI

There is no option to change this configuration using the CLI.

Removing SSL Policy URL categories for Cisco FTD devices managed by FDM Software

To remove the SSL policy URL Category configuration on a device that is managed by Cisco FDM Software, complete the following steps:

Log in to the Cisco FDM web interface.
From the main menu, choose Policies.
Choose the SSL Decryption tab.
For each rule configured, look in the URLs column.
If there is a category listed, then click on the name of the category.
In the pop-up window, click the X next to the name of the category to remove the category
Choose OK.

After changing the policies above, deploy the new policies to your FTD devices.

For detailed information about URL Categories, see the URL Criteria for SSL Decryption Rules https://www.cisco.com/c/en/us/td/docs/security/firepower/730/fdm/fptd-fdm-config-guide-730/fptd-fdm-ssl-decryption.html section in the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

For detailed information about URL filtering, see the URL filtering https://www.cisco.com/c/en/us/td/docs/security/firepower/720/fdm/fptd-fdm-config-guide-720/fptd-fdm-access.html section of the Access Control https://www.cisco.com/c/en/us/td/docs/security/firepower/720/fdm/fptd-fdm-config-guide-720/fptd-fdm-access.html chapter in the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

Removing SSL Policy URL categories for Cisco FTD devices managed by FMC

To remove the SSL policy URL Category configuration on a device that is managed by Cisco FMC Software, complete the following steps:

Log in to the Cisco FMC Software web interface.
From the Policies menu, choose SSL.
Choose the appropriate SSL Policy.
Click the Edit pencil icon.
For each rule configured, look in the Categories column.
If there is a category listed, then click on the name of the category.
In the pop-up window, click the trash can icon to delete the URL category and choose Save.
Choose Save.

After changing the policies above, deploy the new policies to your Cisco FTD devices.

For detailed information about URL Categories, see the Category Rule Conditions https://www.cisco.com/c/en/us/td/docs/security/secure-firewall/management-center/device-config/720/management-center-device-config-72/encrypted-traffic-rules.html section in the Cisco Secure Firewall Management Center Configuration Guide.

For detailed information about URL filtering, see the URL filtering https://www.cisco.com/c/en/us/td/docs/security/secure-firewall/management-center/device-config/720/management-center-device-config-72/access-url-filtering.html section of the Access Control https://www.cisco.com/c/en/us/td/docs/security/secure-firewall/management-center/device-config/720/management-center-device-config-72/access-overview.html chapter in the Cisco Secure Firewall Management Center Configuration Guide.

Removing SSL Policy URL categories for Cisco FTD devices managed by Cisco Discovery Orchestrator

To remove the SSL policy URL Category configuration on a device that is managed by Cisco Discovery Orchestrator, complete the following steps:

Log in to the Cisco Discovery Orchestrator web interface.
From the Cisco Discovery Orchestrator Policies menu, choose FTD Policies.
From the FTD Policies menu, choose Decryption.
Choose the appropriate Decryption Policy.
Click the Edit pencil icon.
For each rule configured, look in the URL column.
If there is a category listed, then click on the name of the category.
In the pop-up window, click the trash can icon to remove the category and choose Save.
Choose Save.

After changing the policies above, deploy the new policies to your Cisco FTD devices.

For detailed information about Cisco Discovery Orchestrator managed devices, see the Cisco Defense Orchestrator documentation. https://docs.defenseorchestrator.com/#!g-managing-security-and-network-devices-with-cdo.html

For detailed information about URL categories, see the Decryption Rules https://www.cisco.com/c/en/us/td/docs/security/cdo/cloud-delivered-firewall-management-center-in-cdo/managing-firewall-threat-defense-services-with-cisco-defense-orchestrator/m_decryption-rules.html chapter of the Managing Firewall Threat Defense with Cloud-Delivered Firewall Management Center in Cisco Defense Orchestrator guide.

For detailed information about URL filtering, see the Access Control https://www.cisco.com/c/en/us/td/docs/security/cdo/cloud-delivered-firewall-management-center-in-cdo/managing-firewall-threat-defense-services-with-cisco-defense-orchestrator/m_access-overview.html chapter of the Managing Firewall Threat Defense with Cloud-Delivered Firewall Management Center in Cisco Defense Orchestrator guide.

For detailed information about URL categories for Cisco FDM Devices managed with Cisco Discovery Orchestrator, see the URL Criteria for SSL Decryption Rules https://www.cisco.com/c/en/us/td/docs/security/cdo/managing-ftd-with-cdo/managing-ftd-with-cisco-defense-orchestrator/configuring-ftd-devices.html section of Managing FDM Devices with Cisco Defense Orchestrator.

For detailed information about URL filtering, see the Access Control https://www.cisco.com/c/en/us/td/docs/security/cdo/managing-ftd-with-cdo/managing-ftd-with-cisco-defense-orchestrator/configuring-ftd-devices.html?bookSearch=true#FTD_Access_Control_Policy section of Managing FDM Devices with Cisco Defense Orchestrator.
Removing SSL Policy from Access Control Policy
Removing SSL Policy from Access Control Policy for Cisco FTD Devices Using the CLI

There is no option to change this configuration using the CLI.

Removing SSL Policy from Access Control Policy for Cisco FTD Devices Managed by FDM Software

To remove the SSL policy URL category configuration on a device that is managed by Cisco FDM Software, complete the following steps:

Log in to the Cisco FDM web interface.
From the main menu, choose Policies.
Choose the SSL Decryption tab.
If SSL Decryption is enabled, disable it.

After changing the policies above, deploy the new policies to your FTD devices.

For detailed information about SSL Decryption, see the SSL Decryption https://www.cisco.com/c/en/us/td/docs/security/firepower/730/fdm/fptd-fdm-config-guide-730/fptd-fdm-ssl-decryption.html chapter in the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

Removing SSL Policy from Access Control Policy for Cisco FTD Devices Managed by FMC

To remove the SSL policy URL category configuration on a device that is managed by Cisco FDM Software, complete the following steps:

Log in to the Cisco FMC Software web interface.
From the Policies menu, choose Access Control.
Choose the appropriate Access Control Policy.
Click the Edit pencil icon.
Look in the SSL Policy area.
If a Policy Name is listed, click on the name.
In the pop-up window, choose None from the drop-down menu and choose OK.
Choose Save.

After changing the policies above, deploy the new policies to your FTD devices.

For detailed information about SSL decryption policies, see the SSL Policy https://www.cisco.com/c/en/us/td/docs/security/secure-firewall/management-center/device-config/720/management-center-device-config-72/encrypted-traffic-policies.html chapter of the Cisco Secure Firewall Management Center Configuration Guide.

Removing SSL Policy from Access Control Policy for Cisco FTD Devices Managed by Cisco Discovery Orchestrator

To remove the SSL policy URL category configuration on a device that is managed by Cisco Discovery Orchestrator, complete the following steps:

Log in to the Cisco Discovery Orchestrator web interface.
From the Cisco Discovery Orchestrator Policies menu, choose FTD Policies.
From the FTD Policies menu, choose Access Control.
Choose the appropriate Access Control Policy.
Click the Edit pencil icon.
Look in the Decryption area.
If there is a policy name in the pop-up window, choose None from the drop-down menu and choose Apply.
Choose Save.

While these workarounds and mitigations have been deployed and were 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.