Cisco Security Advisory
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CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
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A vulnerability in the Simple Network Management Protocol (SNMP) subsystem of Cisco Nexus 9000 Series Fabric Switches in ACI mode could allow an authenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.
This vulnerability is due to improper processing when parsing SNMP requests. An attacker could exploit this vulnerability by continuously sending SNMP queries to a specific MIB of an affected device. A successful exploit could allow the attacker to cause a kernel panic on the device, resulting in a reload and a DoS condition.
Note: This vulnerability affects SNMP versions 1, 2c, and 3. To exploit this vulnerability through SNMPv1 or SNMPv2c, the attacker must have a valid read-only SNMP community string for the affected system. To exploit this vulnerability through SNMPv3, the attacker must have valid SNMP user credentials for the affected system.
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-dsnmp-cNN39UhThis advisory is part of the February 2026 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 2026 Semiannual Cisco FXOS and NX-OS Software Security Advisory Bundled Publication.
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Vulnerable Products
This vulnerability affects Cisco Nexus 9000 Series Fabric Switches in ACI mode when both of the following conditions are met:
- The SNMP feature is enabled.
- At least one authentication, authorization, and accounting (AAA) provider is configured with a DNS name (hostname or fully qualified domain name (FQDN)) or an IPv6 address instead of an IPv4 address.
For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.
Determine the SNMP Configuration
To determine whether a device has SNMPv1, SNMPv2c, or SNMPv3 enabled, use the show snmp summary CLI command from the switch CLI, as shown in the following example:
leaf101# show snmp summary
<Admin State : enabled, running (pid:26630)
Local SNMP engineID: [Hex] 8000000903003A9C451079 [Dec] 128:000:000:009:003:000:058:156:069:016:121
---------------------------------------------------------------------- Community Context Status ---------------------------------------------------------------------- snmp ok
---------------------------------------------------------------------- User Authentication Privacy Status ---------------------------------------------------------------------- snmpv3-user hmac-sha2-256 none okIf the Admin State is enabled and there is an entry under Community (SNMPv1 or SNMPv2c) or User (SNMPv3), SNMP is configured and running. For information regarding SNMP configuration from the Cisco Application Policy Infrastructure Controller (APIC) web UI, see the Configure SNMP in ACI TechNote.
Determine the AAA Configuration
To determine the AAA configuration, use the APIC web UI and complete the following steps:
- Go to Admin > AAA.
- Click Authentication.
- Click Providers.
If any AAA providers are configured with a DNS name (hostname or FQDN) or an IPv6 address instead of an IPv4 address and SNMP is enabled and active, the device is in a vulnerable configuration.
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 3000 Series Switches
- Nexus 5500 Platform Switches
- Nexus 5600 Platform Switches
- Nexus 6000 Series Switches
- Nexus 7000 Series Switches
- Nexus 9000 Series Switches in standalone NX-OS mode
- Secure Firewall 200 Series
- Secure Firewall 1200 Series
- Secure Firewall 3100 Series
- Secure Firewall 4200 Series
- Secure Firewall 6100 Series
- UCS 6300 Series Fabric Interconnects
- UCS 6400 Series Fabric Interconnects
- UCS 6500 Series Fabric Interconnects
- UCS 6600 Series Fabric Interconnects
- UCS X-Series Direct Fabric Interconnects 9108 100G
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This vulnerability causes SNMPd processes to consume memory until an out-of-memory (OOM) condition results in a kernel panic and a device reload. To check for this issue, use the following commands with administrative privileges from the switch CLI.
To check the number of SNMPd processes, use ps -eaf | grep -i snmpd.
Leaf101# ps -eaf | grep snmpd
root 16944 18558 0 Aug08 ? 00:00:00 [snmpd] <defunct>
root 17523 18558 0 Aug08 ? 00:00:00 [snmpd] <defunct>
root 17859 18558 0 Aug08 ? 00:00:00 [snmpd] <defunct>
root 18036 18558 0 Aug08 ? 00:00:00 [snmpd] <defunct>
root 18558 12508 0 Aug08 ? 00:27:50 /isan/bin/snmpd -f -s -d udp:161 udp6:161 tcp:161
root 20075 18558 0 Aug08 ? 00:00:00 /isan/bin/snmpd -f -s -d udp:161 udp6:161 tcp:161If the number of SNMPd processes is more than 10 and is increasing over time, the devices may be impacted by this vulnerability. Processes that show <defunct> do not consume memory but are also a possible indication of this vulnerability.
To get the amount of memory that has been used and is not free, use free -k | awk 'NR==2 {printf "Memory-used: %.2f%%\n", ($2-$7)/$2*100}'.
Leaf101# free -k | awk 'NR==2 {printf "Memory-used: %.2f%%\n", ($2-$7)/$2*100}'
Memory-used: 45.03%If the amount of memory used is more than 85% and is increasing over time, the device is approaching an OOM condition and may reload. The Cisco Technical Assistance Center (TAC) can help to recover a device from the high memory condition.
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A workaround for this vulnerability exists for AAA providers that are configured with IPv4 DNS names. Update all AAA providers from a DNS name (hostname or FQDN) to an IPv4 address configuration. For more information about AAA configuration, see Cisco Application Centric Infrastructure Fundamentals, Release 6.1(x).
There is no workaround for IPv6 configurations.
While this workaround has been deployed and 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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Cisco considers any workarounds and mitigations (if applicable) to be temporary solutions until an upgrade to a fixed software release is available. To fully remediate this vulnerability and avoid future exposure as described in this advisory, Cisco strongly recommends that customers upgrade to the fixed software indicated in this advisory.
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, 10.4(4) for Cisco Nexus 3000 Series Switches or 16.0(8e) for Cisco NX-OS Software in ACI mode.
- Click Check.
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 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 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 2026-FEB-25
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SOFTWARE DOWNLOADS AND TECHNICAL SUPPORT
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. Please note that customers may download only software that was procured from Cisco directly or through a Cisco authorized reseller or partner and for which the license is still valid.
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 Technical Assistance Center (TAC). 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.
When considering software upgrades, customers are advised to regularly consult the advisories for the relevant Cisco products 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.
LEGAL DISCLAIMER DETAILS
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Copies or summaries of the information contained in this Security Advisory may lack important information or contain factual errors. Customers are advised to visit the Cisco Security Advisories page for the most recent version of this Security Advisory. The Cisco Product Security Incident Response Team (PSIRT) assesses only the affected and fixed release information that is documented in this advisory. See the Cisco Security Vulnerability Policy for more information.