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 access control list (ACL) programming of Cisco IOS Software running on Cisco Industrial Ethernet 4000, 4010, and 5000 Series Switches could allow an unauthenticated, remote attacker to bypass a configured ACL.
This vulnerability is due to the incorrect handling of IPv4 ACLs on switched virtual interfaces when an administrator enables and disables Resilient Ethernet Protocol (REP). An attacker could exploit this vulnerability by attempting to send traffic through an affected device. A successful exploit could allow the attacker to bypass an ACL on the affected device.
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-repacl-9eXgnBpDThis advisory is part of the September 2024 release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: September 2024 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication.
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Vulnerable Products
At the time of publication, this vulnerability affected the following Cisco products if they were running Cisco IOS Software Release 15.2(8)E2 or later and had an IPv4 ACL configured on a switched virtual interface (SVI):
- Industrial Ethernet 4000 Series Switches
- Industrial Ethernet 4010 Series Switches
- Industrial Ethernet 5000 Series Switches
Determine the Device Configuration
To determine whether a device has an IPv4 ACL configured on an SVI, use the show running-config | begin ^interface Vlan CLI command. Examine the contents under each SVI (interface Vlan x) to see if an IPv4 access-group has been configured, as shown in the following example:
Switch# show running-config | begin ^interface Vlan
interface Vlan 100
ip address 192.168.1.1 255.255.255.0
ip access-group DropACL in
Switch#Note: This vulnerability becomes exploitable only if the administrator has enabled and disabled REP on an uplink interface. Once it is in a vulnerable state and the ACL is not being evaluated, reload the device to recover and ensure that the ACL is functioning correctly.
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 Cisco products:
- IOS XE Software
- IOS XR Software
- Meraki products
- NX-OS Software
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There are no workarounds that address this vulnerability.
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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 IOS and IOS XE Software
To help customers determine their exposure to vulnerabilities in Cisco IOS and IOS XE 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 determine whether a release is affected by any Cisco Security Advisory. To use the form, follow these steps:
- Choose which advisories the tool will search—only this advisory, only advisories with a Critical or High Security Impact Rating (SIR), or all advisories.
- Enter a release number—for example, 15.9(3)M2 or 17.3.3.
- Click Check.
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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 the resolution of a Cisco TAC support case.
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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-SEP-25
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