Cisco Security Advisory
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CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
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A vulnerability in the Switch Integrated Security Features (SISF) of Cisco IOS Software, Cisco IOS XE Software, Cisco NX-OS Software, and Cisco Wireless LAN Controller (WLC) AireOS Software could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition on an affected device.
This vulnerability is due to the incorrect handling of DHCPv6 packets. An attacker could exploit this vulnerability by sending a crafted DHCPv6 packet to an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.
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-sisf-dos-ZGwt4DdYThis advisory is part of the May 2025 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: May 2025 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication.
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Vulnerable Products
This vulnerability affects Cisco products if they are running a vulnerable release of the following Cisco Software and have SISF enabled:
- IOS Software (CSCwk04230)
- IOS XE Software (CSCvq14413)
- IOS XE Software for WLCs (CSCvo13585)1
- WLC AireOS Software (CSCwj88828)
1. For Cisco IOS XE Software for WLCs, releases 16.11 and earlier are the only vulnerable releases, and they have reached End of Support. See the Fixed Software section of this advisory for more information.
This vulnerability also affects the following Cisco products if they are running a vulnerable release of Cisco NX-OS Software and have SISF enabled:
- Nexus 3000 Series Switches (CSCwk02672)
- Nexus 7000 Series Switches (CSCwk02785)
- Nexus 9000 Series Switches in standalone NX-OS mode (CSCwk02672)
For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.
Determine the Device Configuration
Cisco IOS and IOS XE Software
In Cisco IOS Software and Cisco IOS XE Software, SISF is not enabled by default. To determine whether a device has SISF enabled, use the show device-tracking policies or show ipv6 snooping policies CLI command (it may vary depending on the software release). If there are any policies listed in the output, SISF is enabled. The following examples show samples of the output when these commands are issued on an affected device:
switch# show device-tracking policies
Target Type Policy Feature Target range
vlan 1150 VLAN default Device-tracking vlan all
switch# show ipv6 snooping policies
Target Type Policy Feature Target range
vlan 1150 VLAN default Device-tracking vlan allCisco IOS XE Software for WLCs
In Cisco IOS XE Software for WLCs, SISF is enabled by default. To determine whether a device has SISF enabled, use the show wireless device-tracking database ip CLI command. If there are any entries listed in the output, SISF is enabled, as shown in the following example:
wlc# show wireless device-tracking database ip
IP ZONE/VRF-TABLE-ID STATE DISCOVERY MAC VRF-NAME
--------------------------------------------------------------------------------------
fd12:3456:789a:1::1 0x00000000 Reachable IPv6 NDP aaaa.aaaa.aaaa
10.10.10.20 0x00000000 Reachable IPv4 DHCP bbbb.bbbb.bbbbCisco WLC AireOS Software
In Cisco WLC AireOS Software, a device being affected by this vulnerability depends on the configuration of IPv6. To determine whether a device is affected, use the show ipv6 summary CLI command. If in the output Global Config is marked as enabled, as shown in the following example, the device is affected by this vulnerability:
(controller)> show ipv6 summary
Global Config............................... Enabled
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.Cisco NX-OS Software
In Cisco NX-OS Software, SISF is not enabled by default. To determine whether a device has SISF enabled, use the show ipv6 snooping policies CLI command. If there are any policies listed in the output, SISF is enabled. The following example shows a sample of the output when these commands are issued on an affected device:
switch# show ipv6 snooping policies
Target Type Policy Feature Target range
vlan 100 VLAN dhcpguard-sample-policy DHCP Guard vlan all
vlan 200 VLAN dhcpguard-sample-policy-2 DHCP Guard vlan all
vlan 300 VLAN default Snooping vlan allProducts 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
- IOS XR Software
- MDS 9000 Series Multilayer Switches
- Meraki products
- Nexus 1000 Virtual Edge for VMware vSphere
- Nexus 5500 Platform Switches
- Nexus 5600 Platform Switches
- Nexus 6000 Series Switches
- Nexus 9000 Series Fabric Switches in ACI mode
- Secure Firewall 3100 Series
- Secure Firewall 4200 Series
- UCS 6300 Series Fabric Interconnects
- UCS 6400 Series Fabric Interconnects
- UCS 6500 Series Fabric Interconnects
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There are no workarounds that address this vulnerability.
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Cisco has released free software updates that address the vulnerability described in this advisory. Customers with service contracts that entitle them to regular software updates should obtain security fixes through their usual update channels.
Customers may only install and expect support for software versions and feature sets for which they have purchased a license. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license:
https://www.cisco.com/c/en/us/products/end-user-license-agreement.htmlAdditionally, customers may only download software for which they have a valid license, procured from Cisco directly, or through a Cisco authorized reseller or partner. In most cases this will be a maintenance upgrade to software that was previously purchased. Free security software updates do not entitle customers to a new software license, additional software feature sets, or major revision upgrades.
The Cisco Support and Downloads page on Cisco.com provides information about licensing and downloads. This page can also display customer device support coverage for customers who use the My Devices tool.
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.
Customers Without Service Contracts
Customers who purchase directly from Cisco but do not hold a Cisco service contract and customers who make purchases through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain upgrades by contacting the Cisco TAC: https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html
Customers should have the product serial number available and be prepared to provide the URL of this advisory as evidence of entitlement to a free upgrade.
Fixed Releases
In the following tables, the left column lists Cisco software releases. The right column indicates whether a release is affected by the vulnerability that is described in this advisory and the first release that includes the fix for this vulnerability. Customers are advised to upgrade to an appropriate fixed software release as indicated in this section.
Cisco IOS XE Software for Wireless LAN Controllers Releases First Fixed Release 16.11 and earlier1 Migrate to a fixed release. 16.12 Not vulnerable. 17 Not vulnerable. 1. Cisco IOS XE Software for WLCs releases 16.11 and earlier have reached End of Support. Customers are advised to migrate to a supported release that includes the fix for this vulnerability.Cisco WLC AireOS Software Releases First Fixed Release 8.9 and earlier Migrate to a fixed release. 8.10 8.10.196.0 The Cisco Product Security Incident Response Team (PSIRT) validates only the affected and fixed release information that is documented in this advisory.
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.
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.
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The Cisco 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 2025-MAY-07
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