Cisco Security Advisory
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CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L/E:X/RL:X/RC:X
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A vulnerability in ICMP Version 6 (ICMPv6) processing in Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a slow system memory leak, which over time could lead to a denial of service (DoS) condition.
This vulnerability is due to improper error handling when an IPv6-configured interface receives a specific type of ICMPv6 packet. An attacker could exploit this vulnerability by sending a sustained rate of crafted ICMPv6 packets to a local IPv6 address on a targeted device. A successful exploit could allow the attacker to cause a system memory leak in the ICMPv6 process on the device. As a result, the ICMPv6 process could run out of system memory and stop processing traffic. The device could then drop all ICMPv6 packets, causing traffic instability on the device. Restoring device functionality would require a device reboot.
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-fxos-nxos-icmpv6-dos-YD55jVCq
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Vulnerable Products
At the time of publication, this vulnerability affected the following Cisco products if they were running a vulnerable release of Cisco NX-OS Software and had at least one interface configured for IPv6 traffic:
- MDS 9000 Series Multilayer Switches (CSCvv24541)
- Nexus 1000 Virtual Edge for VMware vSphere (CSCvv96593)
- Nexus 1000V Switch for Microsoft Hyper-V (CSCvv96593)
- Nexus 1000V Switch for VMware vSphere (CSCvv96593)
- Nexus 3000 Series Switches (CSCvv24541)
- Nexus 5500 Platform Switches (CSCvv24541)
- Nexus 5600 Platform Switches (CSCvv24541)
- Nexus 6000 Series Switches (CSCvv24541)
- Nexus 7000 Series Switches (CSCvv24541)
- Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) mode (CSCvv96592)
- Nexus 9000 Series Switches in standalone NX-OS mode (CSCvv24541)
For information about which Cisco software releases were vulnerable at the time of publication, see the Fixed Software section of this advisory. See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information.
Determine the Status of IPv6 on Cisco NX-OS Software
To determine whether a device will accept incoming IPv6 packets, use the show ipv6 interface brief vrf all command at the device CLI. A device could be affected by this vulnerability if the command returns an IPv6 interface status from at least one interface, as shown in the following example:
Switch# show ipv6 interface brief vrf all
IPv6 Interface Status for VRF "default"(1)
Interface IPv6 Address/Link-local Address Interface Status
prot/link/admin
Eth1/65 2001:db8:1:f101::1 up/up/up
fe80::23a:7dff:fe95:d071
IPv6 Interface Status for VRF "management"(2) Interface IPv6 Address/Link-local Address Interface Status
prot/link/adminNote: By default, no IPv6 addresses are enabled in Cisco NX-OS Software. An interface of a Nexus device can be configured with an IPv6 address through the ipv6 address [...] or ipv6 link-local [...] CLI configuration commands. Also, the ipv6 forward CLI configuration command can be used to allow an interface to accept IPv6 packets even if no IPv6 address is configured.
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
- UCS 6200 Series Fabric Interconnects
- UCS 6300 Series Fabric Interconnects
- UCS 6400 Series Fabric Interconnects
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This vulnerability causes a system memory leak in the ICMPv6 process. ICMPv6 memory exhaustion can result in device instability. The following indicators of compromise that may occur if this vulnerability is being actively exploited.
Contact the Cisco Technical Assistance Center (TAC) if additional help is needed to determine whether this vulnerability may have been exploited on the device.
Memory Allocation
Exploitation of this vulnerability will cause the IPCMPv6 process to continue allocating memory until the memory limit is reached. This memory is not returned, and a device reboot is required to recover. Use the show processes memory sort command at the CLI to monitor the MemUsed field. The command output also shows the memory limit.
nxos# show processes memory sort
PID MemAlloc MemLimit MemUsed StackBase/Ptr Process
----- -------- ---------- ---------- ----------------- -----------
7073 561393664 1067925798 1152303104 ffc80440/ffc7fed0 icmpv6If the show processes memory sort command is not available, use the show processes memory | include icmpv6 command at the CLI:
nxos# show processes memory | include icmpv6
PID MemAlloc MemLimit MemUsed StackBase/Ptr Process
----- -------- ---------- ---------- ----------------- -----------
27418 26259456 1366538124 1000681472 ffca1d60/ffca1800 icmpv6ICMPv6 Errors
Monitor for syslog messages about ICMPv6 errors, such as the two that follow:
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%ICMPV6-3-ATIMERS_ERROR: malloc failed in heap_create -
%ICMPV6-3-ERROR: -Traceback: librsw.so+0x11250e librs w.so+0x10be66 libam.so+0xd7f3 libam.so+0xe4cd icmpv6=0x1004f000 0x100ed1b9 0x101 05623 0x10078fe7 libipv6.so+0x14988 librsw.so+0xc8658 libpthread.so.0+0x609b lib c.so.6+0xd6a5e
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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 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 to identify any Cisco Security Advisories that impact a specific Cisco NX-OS 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 identified (“Combined First Fixed”).
Customers can use the Cisco Software Checker to search advisories in the following ways:
- Choose the software, platform, and one or more releases
- Upload a .txt file that includes a list of specific releases
- Enter the output of the show version command
After initiating a search, customers can customize the search to include all Cisco Security Advisories or one or more specific advisories.
Customers can also use the following form to determine whether a release is affected by any Cisco Security Advisory by choosing the Cisco NX-OS Software and platform and then entering a release—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:
By default, the Cisco Software Checker includes results only for vulnerabilities that have a Critical or High Security Impact Rating (SIR). To include results for Medium SIR vulnerabilities, customers can use the Cisco Software Checker and check the Medium check box in the drop-down list under Impact Rating when customizing a search.
Cisco Nexus 7000 Series Switches SMUs
For Cisco Nexus 7000 Series Switches, software maintenance upgrades (SMUs) are available for Cisco NX-OS Software Release 8.2(6). Customers can download the following SMUs from the Software Center on Cisco.com:
- n7000-s2-dk9.8.2.6.CSCvx15395.bin
- n7700-s2-dk9.8.2.6.CSCvx15395.bin
For details about downloading and installing SMUs in Cisco NX-OS Software for Cisco Nexus 7000 Series Switches, see the Performing Software Maintenance Upgrades section of the Cisco Nexus 7000 Series NX-OS System Management Configuration Guide.
See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information.
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.
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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 2021-FEB-24
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