Multiple Cisco Products Snort Rule Denial of Service Vulnerability
Multiple Cisco products are affected by a vulnerability in Snort rules that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to improper handling of the Block with Reset or Interactive Block with Reset actions if a rule is configured without proper constraints. An attacker could exploit this vulnerability by sending a crafted IP packet to the affected device. A successful exploit could allow the attacker to cause through traffic to be dropped. Note: Only products with Snort3 configured and either a rule with Block with Reset or Interactive Block with Reset actions configured are vulnerable. Products configured with Snort2 are not vulnerable. Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability. This advisory is part of the October 2021 release of the Cisco ASA, FTD, and FMC Security Advisory Bundled publication. For a complete list of the advisories and links to them, see Cisco Event Response: October 2021 Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication ["https://sec.cloudapps.cisco.com/security/center/viewErp.x?alertId=ERP-74773"].
describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2021-40116US | high7.5 | — | ||
Multiple Cisco products are affected by a vulnerability in Snort rules that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affec… | ||||
references
External citations — patches, advisories, analysis.
- Multiple Cisco Products Snort Rule Denial of Service Vulnerabilityself
- Cisco Security Vulnerability Policyexternal
- considering software upgradesexternal
- Cisco Event Response: October 2021 Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publicationexternal
- https://www.cisco.com/c/en/us/products/end-user-license-agreement.htmlexternal
- end of software maintenanceexternal
- https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.htmlexternal
- Cisco Firepower Management Center Upgrade Guideexternal
remediations (24)
- FixedCisco Secure Firewall Threat Defense (FTD) Software 7.0.0 when installed on Cisco 3000 Series Industrial Security Appliances (ISA)
Cisco has released software updates that address this vulnerability.
https://software.cisco.com - FixedCisco Secure Firewall Threat Defense (FTD) Software 7.0.0 when installed on Cisco Firepower 1000 Series
Cisco has released software updates that address this vulnerability.
https://software.cisco.com - FixedCisco Secure Firewall Threat Defense (FTD) Software 7.0.0 when installed on Cisco Firepower 2100 Series
Cisco has released software updates that address this vulnerability.
https://software.cisco.com - FixedCisco Secure Firewall Threat Defense (FTD) Software 7.0.0 when installed on Cisco Firepower 4100 Series
Cisco has released software updates that address this vulnerability.
https://software.cisco.com - FixedCisco Secure Firewall Threat Defense (FTD) Software 7.0.0 when installed on Cisco Firepower 9000 Series
Cisco has released software updates that address this vulnerability.
https://software.cisco.com - FixedCisco Secure Firewall Threat Defense (FTD) Software 7.0.0 when installed on Cisco Secure Firewall Threat Defense Virtual
Cisco has released software updates that address this vulnerability.
https://software.cisco.com - FixedCisco Secure Firewall Threat Defense (FTD) Software 7.0.0.1 when installed on Cisco 3000 Series Industrial Security Appliances (ISA)
Cisco has released software updates that address this vulnerability.
https://software.cisco.com - FixedCisco Secure Firewall Threat Defense (FTD) Software 7.0.0.1 when installed on Cisco Firepower 1000 Series
Cisco has released software updates that address this vulnerability.
https://software.cisco.com - FixedCisco Secure Firewall Threat Defense (FTD) Software 7.0.0.1 when installed on Cisco Firepower 2100 Series
Cisco has released software updates that address this vulnerability.
https://software.cisco.com - FixedCisco Secure Firewall Threat Defense (FTD) Software 7.0.0.1 when installed on Cisco Firepower 4100 Series
Cisco has released software updates that address this vulnerability.
https://software.cisco.com - FixedCisco Secure Firewall Threat Defense (FTD) Software 7.0.0.1 when installed on Cisco Firepower 9000 Series
Cisco has released software updates that address this vulnerability.
https://software.cisco.com - FixedCisco Secure Firewall Threat Defense (FTD) Software 7.0.0.1 when installed on Cisco Secure Firewall Threat Defense Virtual
Cisco has released software updates that address this vulnerability.
https://software.cisco.com - WorkaroundCisco Secure Firewall Threat Defense (FTD) Software 7.0.0 when installed on Cisco 3000 Series Industrial Security Appliances (ISA)
There are workarounds that addresses this vulnerability. While these workarounds 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. Note: There are three workarounds for this issue. Implementing any of the workarounds is sufficient. Two or more workarounds do not need to be implemented. Workaround 1 The first workaround is to change the Snort inspection engine from Snort3 to Snort2. See the configuration guide or support team for potential impacts. The steps to revert to Snort2 are as follows: Go to the FMC web interface Go to the Devices page and then the Device Management tab. Select the FTD device to check. Choose Edit. Go to the Device tab and look in the Inspection Engine area. Choose the Revert to Snort2 option. Workaround 2 The second workaround is to change all rule actions from Block with Reset or Interactive Block with Reset to another action. See the configuration guide or support team for potential impacts. The steps are as follows: Go to the FMC web interface Go to the Policies page and then the Access Control tab. Select the Policy to review and choose Edit. Find a rule that has a Reset action and choose Edit. Change the action from Block with Reset or Interactive Block with Reset to another action. Workaround 3 The third workaround involves narrowing the firewall reset rule to block TCP and/or UDP directly or by specifying an application that runs over UDP or TCP. See the Vulnerable Products ["#vp"] section for examples of vulnerable and non-vulnerable configurations.
- WorkaroundCisco Secure Firewall Threat Defense (FTD) Software 7.0.0 when installed on Cisco Firepower 1000 Series
There are workarounds that addresses this vulnerability. While these workarounds 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. Note: There are three workarounds for this issue. Implementing any of the workarounds is sufficient. Two or more workarounds do not need to be implemented. Workaround 1 The first workaround is to change the Snort inspection engine from Snort3 to Snort2. See the configuration guide or support team for potential impacts. The steps to revert to Snort2 are as follows: Go to the FMC web interface Go to the Devices page and then the Device Management tab. Select the FTD device to check. Choose Edit. Go to the Device tab and look in the Inspection Engine area. Choose the Revert to Snort2 option. Workaround 2 The second workaround is to change all rule actions from Block with Reset or Interactive Block with Reset to another action. See the configuration guide or support team for potential impacts. The steps are as follows: Go to the FMC web interface Go to the Policies page and then the Access Control tab. Select the Policy to review and choose Edit. Find a rule that has a Reset action and choose Edit. Change the action from Block with Reset or Interactive Block with Reset to another action. Workaround 3 The third workaround involves narrowing the firewall reset rule to block TCP and/or UDP directly or by specifying an application that runs over UDP or TCP. See the Vulnerable Products ["#vp"] section for examples of vulnerable and non-vulnerable configurations.
- WorkaroundCisco Secure Firewall Threat Defense (FTD) Software 7.0.0 when installed on Cisco Firepower 2100 Series
There are workarounds that addresses this vulnerability. While these workarounds 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. Note: There are three workarounds for this issue. Implementing any of the workarounds is sufficient. Two or more workarounds do not need to be implemented. Workaround 1 The first workaround is to change the Snort inspection engine from Snort3 to Snort2. See the configuration guide or support team for potential impacts. The steps to revert to Snort2 are as follows: Go to the FMC web interface Go to the Devices page and then the Device Management tab. Select the FTD device to check. Choose Edit. Go to the Device tab and look in the Inspection Engine area. Choose the Revert to Snort2 option. Workaround 2 The second workaround is to change all rule actions from Block with Reset or Interactive Block with Reset to another action. See the configuration guide or support team for potential impacts. The steps are as follows: Go to the FMC web interface Go to the Policies page and then the Access Control tab. Select the Policy to review and choose Edit. Find a rule that has a Reset action and choose Edit. Change the action from Block with Reset or Interactive Block with Reset to another action. Workaround 3 The third workaround involves narrowing the firewall reset rule to block TCP and/or UDP directly or by specifying an application that runs over UDP or TCP. See the Vulnerable Products ["#vp"] section for examples of vulnerable and non-vulnerable configurations.
- WorkaroundCisco Secure Firewall Threat Defense (FTD) Software 7.0.0 when installed on Cisco Firepower 4100 Series
There are workarounds that addresses this vulnerability. While these workarounds 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. Note: There are three workarounds for this issue. Implementing any of the workarounds is sufficient. Two or more workarounds do not need to be implemented. Workaround 1 The first workaround is to change the Snort inspection engine from Snort3 to Snort2. See the configuration guide or support team for potential impacts. The steps to revert to Snort2 are as follows: Go to the FMC web interface Go to the Devices page and then the Device Management tab. Select the FTD device to check. Choose Edit. Go to the Device tab and look in the Inspection Engine area. Choose the Revert to Snort2 option. Workaround 2 The second workaround is to change all rule actions from Block with Reset or Interactive Block with Reset to another action. See the configuration guide or support team for potential impacts. The steps are as follows: Go to the FMC web interface Go to the Policies page and then the Access Control tab. Select the Policy to review and choose Edit. Find a rule that has a Reset action and choose Edit. Change the action from Block with Reset or Interactive Block with Reset to another action. Workaround 3 The third workaround involves narrowing the firewall reset rule to block TCP and/or UDP directly or by specifying an application that runs over UDP or TCP. See the Vulnerable Products ["#vp"] section for examples of vulnerable and non-vulnerable configurations.
- WorkaroundCisco Secure Firewall Threat Defense (FTD) Software 7.0.0 when installed on Cisco Firepower 9000 Series
There are workarounds that addresses this vulnerability. While these workarounds 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. Note: There are three workarounds for this issue. Implementing any of the workarounds is sufficient. Two or more workarounds do not need to be implemented. Workaround 1 The first workaround is to change the Snort inspection engine from Snort3 to Snort2. See the configuration guide or support team for potential impacts. The steps to revert to Snort2 are as follows: Go to the FMC web interface Go to the Devices page and then the Device Management tab. Select the FTD device to check. Choose Edit. Go to the Device tab and look in the Inspection Engine area. Choose the Revert to Snort2 option. Workaround 2 The second workaround is to change all rule actions from Block with Reset or Interactive Block with Reset to another action. See the configuration guide or support team for potential impacts. The steps are as follows: Go to the FMC web interface Go to the Policies page and then the Access Control tab. Select the Policy to review and choose Edit. Find a rule that has a Reset action and choose Edit. Change the action from Block with Reset or Interactive Block with Reset to another action. Workaround 3 The third workaround involves narrowing the firewall reset rule to block TCP and/or UDP directly or by specifying an application that runs over UDP or TCP. See the Vulnerable Products ["#vp"] section for examples of vulnerable and non-vulnerable configurations.
- WorkaroundCisco Secure Firewall Threat Defense (FTD) Software 7.0.0 when installed on Cisco Secure Firewall Threat Defense Virtual
There are workarounds that addresses this vulnerability. While these workarounds 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. Note: There are three workarounds for this issue. Implementing any of the workarounds is sufficient. Two or more workarounds do not need to be implemented. Workaround 1 The first workaround is to change the Snort inspection engine from Snort3 to Snort2. See the configuration guide or support team for potential impacts. The steps to revert to Snort2 are as follows: Go to the FMC web interface Go to the Devices page and then the Device Management tab. Select the FTD device to check. Choose Edit. Go to the Device tab and look in the Inspection Engine area. Choose the Revert to Snort2 option. Workaround 2 The second workaround is to change all rule actions from Block with Reset or Interactive Block with Reset to another action. See the configuration guide or support team for potential impacts. The steps are as follows: Go to the FMC web interface Go to the Policies page and then the Access Control tab. Select the Policy to review and choose Edit. Find a rule that has a Reset action and choose Edit. Change the action from Block with Reset or Interactive Block with Reset to another action. Workaround 3 The third workaround involves narrowing the firewall reset rule to block TCP and/or UDP directly or by specifying an application that runs over UDP or TCP. See the Vulnerable Products ["#vp"] section for examples of vulnerable and non-vulnerable configurations.
- WorkaroundCisco Secure Firewall Threat Defense (FTD) Software 7.0.0.1 when installed on Cisco 3000 Series Industrial Security Appliances (ISA)
There are workarounds that addresses this vulnerability. While these workarounds 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. Note: There are three workarounds for this issue. Implementing any of the workarounds is sufficient. Two or more workarounds do not need to be implemented. Workaround 1 The first workaround is to change the Snort inspection engine from Snort3 to Snort2. See the configuration guide or support team for potential impacts. The steps to revert to Snort2 are as follows: Go to the FMC web interface Go to the Devices page and then the Device Management tab. Select the FTD device to check. Choose Edit. Go to the Device tab and look in the Inspection Engine area. Choose the Revert to Snort2 option. Workaround 2 The second workaround is to change all rule actions from Block with Reset or Interactive Block with Reset to another action. See the configuration guide or support team for potential impacts. The steps are as follows: Go to the FMC web interface Go to the Policies page and then the Access Control tab. Select the Policy to review and choose Edit. Find a rule that has a Reset action and choose Edit. Change the action from Block with Reset or Interactive Block with Reset to another action. Workaround 3 The third workaround involves narrowing the firewall reset rule to block TCP and/or UDP directly or by specifying an application that runs over UDP or TCP. See the Vulnerable Products ["#vp"] section for examples of vulnerable and non-vulnerable configurations.
- WorkaroundCisco Secure Firewall Threat Defense (FTD) Software 7.0.0.1 when installed on Cisco Firepower 1000 Series
There are workarounds that addresses this vulnerability. While these workarounds 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. Note: There are three workarounds for this issue. Implementing any of the workarounds is sufficient. Two or more workarounds do not need to be implemented. Workaround 1 The first workaround is to change the Snort inspection engine from Snort3 to Snort2. See the configuration guide or support team for potential impacts. The steps to revert to Snort2 are as follows: Go to the FMC web interface Go to the Devices page and then the Device Management tab. Select the FTD device to check. Choose Edit. Go to the Device tab and look in the Inspection Engine area. Choose the Revert to Snort2 option. Workaround 2 The second workaround is to change all rule actions from Block with Reset or Interactive Block with Reset to another action. See the configuration guide or support team for potential impacts. The steps are as follows: Go to the FMC web interface Go to the Policies page and then the Access Control tab. Select the Policy to review and choose Edit. Find a rule that has a Reset action and choose Edit. Change the action from Block with Reset or Interactive Block with Reset to another action. Workaround 3 The third workaround involves narrowing the firewall reset rule to block TCP and/or UDP directly or by specifying an application that runs over UDP or TCP. See the Vulnerable Products ["#vp"] section for examples of vulnerable and non-vulnerable configurations.
- WorkaroundCisco Secure Firewall Threat Defense (FTD) Software 7.0.0.1 when installed on Cisco Firepower 2100 Series
There are workarounds that addresses this vulnerability. While these workarounds 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. Note: There are three workarounds for this issue. Implementing any of the workarounds is sufficient. Two or more workarounds do not need to be implemented. Workaround 1 The first workaround is to change the Snort inspection engine from Snort3 to Snort2. See the configuration guide or support team for potential impacts. The steps to revert to Snort2 are as follows: Go to the FMC web interface Go to the Devices page and then the Device Management tab. Select the FTD device to check. Choose Edit. Go to the Device tab and look in the Inspection Engine area. Choose the Revert to Snort2 option. Workaround 2 The second workaround is to change all rule actions from Block with Reset or Interactive Block with Reset to another action. See the configuration guide or support team for potential impacts. The steps are as follows: Go to the FMC web interface Go to the Policies page and then the Access Control tab. Select the Policy to review and choose Edit. Find a rule that has a Reset action and choose Edit. Change the action from Block with Reset or Interactive Block with Reset to another action. Workaround 3 The third workaround involves narrowing the firewall reset rule to block TCP and/or UDP directly or by specifying an application that runs over UDP or TCP. See the Vulnerable Products ["#vp"] section for examples of vulnerable and non-vulnerable configurations.
- WorkaroundCisco Secure Firewall Threat Defense (FTD) Software 7.0.0.1 when installed on Cisco Firepower 4100 Series
There are workarounds that addresses this vulnerability. While these workarounds 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. Note: There are three workarounds for this issue. Implementing any of the workarounds is sufficient. Two or more workarounds do not need to be implemented. Workaround 1 The first workaround is to change the Snort inspection engine from Snort3 to Snort2. See the configuration guide or support team for potential impacts. The steps to revert to Snort2 are as follows: Go to the FMC web interface Go to the Devices page and then the Device Management tab. Select the FTD device to check. Choose Edit. Go to the Device tab and look in the Inspection Engine area. Choose the Revert to Snort2 option. Workaround 2 The second workaround is to change all rule actions from Block with Reset or Interactive Block with Reset to another action. See the configuration guide or support team for potential impacts. The steps are as follows: Go to the FMC web interface Go to the Policies page and then the Access Control tab. Select the Policy to review and choose Edit. Find a rule that has a Reset action and choose Edit. Change the action from Block with Reset or Interactive Block with Reset to another action. Workaround 3 The third workaround involves narrowing the firewall reset rule to block TCP and/or UDP directly or by specifying an application that runs over UDP or TCP. See the Vulnerable Products ["#vp"] section for examples of vulnerable and non-vulnerable configurations.
- WorkaroundCisco Secure Firewall Threat Defense (FTD) Software 7.0.0.1 when installed on Cisco Firepower 9000 Series
There are workarounds that addresses this vulnerability. While these workarounds 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. Note: There are three workarounds for this issue. Implementing any of the workarounds is sufficient. Two or more workarounds do not need to be implemented. Workaround 1 The first workaround is to change the Snort inspection engine from Snort3 to Snort2. See the configuration guide or support team for potential impacts. The steps to revert to Snort2 are as follows: Go to the FMC web interface Go to the Devices page and then the Device Management tab. Select the FTD device to check. Choose Edit. Go to the Device tab and look in the Inspection Engine area. Choose the Revert to Snort2 option. Workaround 2 The second workaround is to change all rule actions from Block with Reset or Interactive Block with Reset to another action. See the configuration guide or support team for potential impacts. The steps are as follows: Go to the FMC web interface Go to the Policies page and then the Access Control tab. Select the Policy to review and choose Edit. Find a rule that has a Reset action and choose Edit. Change the action from Block with Reset or Interactive Block with Reset to another action. Workaround 3 The third workaround involves narrowing the firewall reset rule to block TCP and/or UDP directly or by specifying an application that runs over UDP or TCP. See the Vulnerable Products ["#vp"] section for examples of vulnerable and non-vulnerable configurations.
- WorkaroundCisco Secure Firewall Threat Defense (FTD) Software 7.0.0.1 when installed on Cisco Secure Firewall Threat Defense Virtual
There are workarounds that addresses this vulnerability. While these workarounds 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. Note: There are three workarounds for this issue. Implementing any of the workarounds is sufficient. Two or more workarounds do not need to be implemented. Workaround 1 The first workaround is to change the Snort inspection engine from Snort3 to Snort2. See the configuration guide or support team for potential impacts. The steps to revert to Snort2 are as follows: Go to the FMC web interface Go to the Devices page and then the Device Management tab. Select the FTD device to check. Choose Edit. Go to the Device tab and look in the Inspection Engine area. Choose the Revert to Snort2 option. Workaround 2 The second workaround is to change all rule actions from Block with Reset or Interactive Block with Reset to another action. See the configuration guide or support team for potential impacts. The steps are as follows: Go to the FMC web interface Go to the Policies page and then the Access Control tab. Select the Policy to review and choose Edit. Find a rule that has a Reset action and choose Edit. Change the action from Block with Reset or Interactive Block with Reset to another action. Workaround 3 The third workaround involves narrowing the firewall reset rule to block TCP and/or UDP directly or by specifying an application that runs over UDP or TCP. See the Vulnerable Products ["#vp"] section for examples of vulnerable and non-vulnerable configurations.
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