Cisco Security Advisory
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CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N/E:X/RL:X/RC:X
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A vulnerability in the activation of an access control list (ACL) on Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to bypass the protection that is offered by a configured ACL on an affected device.
This vulnerability is due to a logic error that occurs when an ACL changes from inactive to active in the running configuration of an affected device. An attacker could exploit this vulnerability by sending traffic through the affected device that should be denied by the configured ACL. The reverse condition is also true—traffic that should be permitted could be denied by the configured ACL. A successful exploit could allow the attacker to bypass configured ACL protections on the affected device, allowing the attacker to access trusted networks that the device might be protecting.
Note: This vulnerability applies to both IPv4 and IPv6 traffic as well as dual-stack ACL configurations in which both IPv4 and IPv6 ACLs are configured on an interface.
Cisco has released software updates that address this vulnerability. There is a workaround that addresses this vulnerability.
This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-ogsnsg-aclbyp-3XB8q6jXThis advisory is part of the May 2024 release of the Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: May 2024 Semiannual Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication.
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Vulnerable Products
At the time of publication, this vulnerability affected Cisco products if they were running one of the following Cisco software releases with a vulnerable configuration:
- ASA Software releases 9.19.1 to 9.19.1.24, 9.20.1, or 9.20.1.5
- FTD Software releases 7.3.0 to 7.4.0
For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.
Determine Whether the Device Has a Vulnerable Configuration
This ACL bypass vulnerability is the result of a specific configuration and requires changing an access list from inactive to active. A vulnerable configuration must meet the following conditions:
- The object group search (OGS) ACL optimization feature is enabled, as shown by the object-group-search access-control command in the running-config example that follows this bulleted list.
- An access list that is configured as inactive does not have object group network service (NSG)1 but does contain a network object group. In the following example, the network object group is sample1.
If the above two conditions are met and the access list is changed from inactive to active, the change does not take effect, and there is no warning to the user. In the following example, the access list is CSM_FW_ACL_.
In the following example, which shows a snippet of this configuration, access list CSM_FW_ACL_ would fail to become active, which would result in traffic failing to match that rule.
device# show running-config
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object-group-search access-control
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object-group network sample1
network-object host 192.168.1.2
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access-group CSM_FW_ACL_ global
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access-list CSM_FW_ACL_ extended permit ip host 192.168.1.1 object-group sample1 inactive
access-group CSM_FW_ACL_ global
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.1. For information about the NSG configuration, see Cisco Secure Firewall ASA Series Command Reference, I - R Commands : object network-service.
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 Cisco Firepower Management Center (FMC) Software.
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There is a workaround that addresses this vulnerability. The access list that is not working can be removed and reconfigured to work around this vulnerability. Use the example configuration from the Vulnerable Products section of this advisory to execute the following CLI commands:
device# no access-list CSM_FW_ACL_ extended permit ip host 192.168.1.1 object-group sample1
device# access-list CSM_FW_ACL_ extended permit ip host 192.168.1.1 object-group sample1While 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.
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When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories page, to determine exposure and a complete upgrade solution.
In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.
Cisco ASA, FMC, and FTD Software
To help customers determine their exposure to vulnerabilities in Cisco ASA, FMC, and 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:
- Choose which advisories the tool will search—all advisories, only advisories with a Critical or High Security Impact Rating (SIR), or only this advisory.
- Choose the appropriate software.
- Choose the appropriate platform.
- Enter a release number—for example, 9.16.2.11 for Cisco ASA Software or 6.6.7 for Cisco FTD Software.
- Click Check.
For instructions on upgrading an FTD device, see Cisco Firepower Management Center Upgrade Guide.
Additional Resources
For help determining the best Cisco ASA, FMC, or FTD Software release, see the following Recommended Releases documents. If a security advisory recommends a later release, Cisco recommends following the advisory guidance.
Cisco ASA Compatibility
Cisco Secure Firewall ASA Upgrade Guide
Cisco Secure Firewall Threat Defense Compatibility Guide
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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.
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This vulnerability was found during internal security testing.
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To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
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Show LessVersion Description Section Status Date 1.0 Initial public release. — Final 2024-MAY-22
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