Cisco Security Advisory
Click Icon to Copy Verbose Score
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
-
A vulnerability in the access control list (ACL) programming for port channel subinterfaces of Cisco Nexus 3000 and 9000 Series Switches in standalone NX-OS mode could allow an unauthenticated, remote attacker to send traffic that should be blocked through an affected device.
This vulnerability is due to incorrect hardware programming that occurs when configuration changes are made to port channel member ports. An attacker could exploit this vulnerability by attempting to send traffic through an affected device. A successful exploit could allow the attacker to access network resources that should be protected by an ACL that was applied on port channel subinterfaces.
Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability.
This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-po-acl-TkyePgvLThis advisory is part of the February 2024 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: February 2024 Semiannual Cisco FXOS and NX-OS Software Security Advisory Bundled Publication.
-
Vulnerable Products
At the time of publication, this vulnerability affected Cisco Nexus 3000 and 9000 Series Switches in standalone NX-OS mode if they were running Cisco NX-OS Software Release 9.3(10), 9.3(11), or 9.3(12) and had an ingress ACL configured on at least one port channel subinterface, as shown in the following example:
nxos# show running-config interface port-channel 10.10
interface port-channel10.10
encapsulation dot1q 10
ip access-group acl-10 in
ip address 10.10.1.1/24
no shutdownNote: When using an affected configuration, any changes made to port channel member ports may result in ACL programming errors.
Determine Whether the ACL Programming is Affected
To determine whether the ACL programming is affected, use the show system internal access-list interface port-channel subinterface input entries detail command at the device CLI. In a regular ACL programming situation, the command is expected to return ACL entries that are associated to the subinterface in question, as seen in the following example:
nxos# show system internal access-list interface port-channel 10.10 input entries detail
slot 1
=======
Flags: F - Fragment entry E - Port Expansion
D - DSCP Expansion M - ACL Expansion
T - Cross Feature Merge Expansion
N - NS Transit B - BCM Expansion C - COPP
INSTANCE 0x0
---------------
Tcam 1 resource usage:
----------------------
LBL B = 0xa
Bank 1
------
IPv4 Class
Policies: RACL(acl-10)
Netflow profile: 0
Netflow deny profile: 0
Entries:
[Index] Entry [Stats]
---------------------
[0x001c:0x001e:0x001e] permit ip 0.0.0.0/0 10.10.1.11/32 routeable 0x1 [0]
[0x001d:0x001f:0x001f] deny ip 0.0.0.0/0 10.10.1.12/32 routeable 0x1 [0]
[0x001e:0x0020:0x0020] deny ip 0.0.0.0/0 0.0.0.0/0 routeable 0x1 [0]If the command returns no entries for a port channel subinterface that is configured with an access list, ACL programming is affected, as seen in the following example:
nxos# show system internal access-list interface port-channel 10.10 input entries detail
slot 1
=======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:
- Firepower 1000 Series
- Firepower 2100 Series
- Firepower 4100 Series
- Firepower 9300 Security Appliances
- MDS 9000 Series Multilayer Switches
- Nexus 1000 Virtual Edge for VMware vSphere
- Nexus 1000V Switch for Microsoft Hyper-V
- Nexus 1000V Switch for VMware vSphere
- Nexus 5500 Platform Switches
- Nexus 5600 Platform Switches
- Nexus 6000 Series Switches
- Nexus 7000 Series Switches
- Nexus 9000 Series Fabric Switches in ACI mode
- Secure Firewall 3100 Series
- Secure Firewall 4200 Series
- UCS 6200 Series Fabric Interconnects
- UCS 6300 Series Fabric Interconnects
- UCS 6400 Series Fabric Interconnects
- UCS 6500 Series Fabric Interconnects
-
There are workarounds that address this vulnerability.
After performing configuration changes to port channel member ports, verify whether the ACL programming is affected on any port channel subinterface, as shown in the Vulnerable Products section of this advisory. Proper ACL programming can be restored on any affected port channel subinterface by removing and reapplying the associated ip access-group configuration command. Reloading an affected device would also fix the ACL programming for all affected subinterfaces.
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.
-
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 NX-OS Software
To help customers determine their exposure to vulnerabilities in Cisco NX-OS 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 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—only this advisory, only advisories with a Critical or High Security Impact Rating (SIR), or all advisories.
- Choose the appropriate software.
- Choose the appropriate platform.
- Enter a release number—for example, 7.0(3)I7(5) for Cisco Nexus 3000 Series Switches or 14.0(1h) for Cisco NX-OS Software in ACI mode.
- Click Check.
Cisco Nexus 3000 and 9000 Series Switches SMUs
Cisco has released the following SMU to address this vulnerability. Customers can download the SMU from the Software Center on Cisco.com.
Cisco NX-OS Software Release Platform SMU Name 9.3(12) Nexus 3000 and 9000 Series Switches nxos.CSCwf47127-n9k_ALL-1.0.0-9.3.12.lib32_n9000.rpm For details about downloading and installing SMUs in Cisco NX-OS Software for Cisco Nexus 3000 and 9000 Series Switches, see the Performing Software Maintenance Upgrades section of the Cisco NX-OS system management configuration guide for Cisco Nexus 3000 Series Switches and Cisco Nexus 9000 Series Switches.
Additional Resources
For help determining the best Cisco NX-OS Software release for a Cisco Nexus Switch, see the following Recommended Releases documents. If a security advisory recommends a later release, Cisco recommends following the advisory guidance.
Cisco MDS Series Switches
Cisco Nexus 1000V for VMware Switch
Cisco Nexus 3000 Series Switches
Cisco Nexus 5500 Platform Switches
Cisco Nexus 5600 Platform Switches
Cisco Nexus 6000 Series Switches
Cisco Nexus 7000 Series Switches
Cisco Nexus 9000 Series Switches
Cisco Nexus 9000 Series ACI-Mode SwitchesTo determine the best release for Cisco UCS Software, see the Recommended Releases documents in the release notes for the device.
-
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.
-
This vulnerability was found during internal security testing.
-
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.
-
Show LessVersion Description Section Status Date 1.0 Initial public release. — Final 2024-FEB-28
-
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.
A standalone copy or paraphrase of the text of this document that omits the distribution URL is an uncontrolled copy and may lack important information or contain factual errors. The information in this document is intended for end users of Cisco products.