Summary

• A vulnerability in the Silicon One integration for Cisco Nexus 9000 Series Switches could allow an unauthenticated, remote attacker to execute code with root privileges.

  This vulnerability exists because TCP ports 43210 and 43211 are accessible in the default Layer 3 (L3) virtual routing and forwarding (VRF). A successful exploit could allow the attacker to connect to an affected device and send crafted input that could be executed as code with root privileges. The exploitation of this vulnerability could also cause the S1HAL process to crash, which could cause the device to reload.

  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-n9k-s1-rce-EH8dEtr

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco Nexus 9000 Series Switches if they include a Silicon One ASIC.

  For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.

  At the time of publication, Cisco Nexus 9000 Series Switches with the following product identifiers (PIDs) included a Silicon One ASIC:

  • N9324C-SE1U
  • N9348Y2C6D-SE1U
  • N9364E-SG2-O
  • N9364E-SG2-Q
  • N9396T12C-SE1
  • N9348Y12C-SE1
  • N9396Y12C-SE1
  • N9336C-SE1
  • N9K-C9804
  • N9K-C9808

  To determine the PID for a device, use the show module CLI command. In the following example, the PID of the device is N9336C-SE1, which is on the list of devices that are affected by this vulnerability.

  switch# show module
  Mod Ports                  Module-Type                            Model           Status
  --- ----- ------------------------------------------------ --------------------- --------
  1    36   36x40/100G QSFP28 Ethernet Module                N9336C-SE1            ok  

  
  

  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 7000 Series Switches
  • Nexus 9000 Series Switches other than the models listed in the Vulnerable Products section
  • Nexus 9000 Series Fabric Switches in ACI 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 Interconnect 9108 100G

Workarounds

• There is a workaround that addresses this vulnerability.

  To prevent remote exploitation of this vulnerability, use infrastructure access control lists (iACLs) to allow only required management and control plane traffic that is destined to the affected device. Alternatively, the iACLs may be used to explicitly deny all TCP packets that are destined to a locally configured IP address with a destination port of 43210 or 43211.

  For more information about iACLs, see the Cisco NX-OS Software Hardening Guide.

  While this workaround has been deployed and was 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.

  Live Protect Shields

  Cisco has released a Live Protect shield for CVE-2026-20212 to temporarily mitigate this vulnerability in Cisco NX-OS Software.

  For information about Live Protect for Cisco NX-OS Software, see Cisco Nexus 9000 Series NX-OS Security Configuration Guide.

  Note: Live Protect shields are temporary mitigations to bridge the gap until software updates can be scheduled. To fully remediate this vulnerability, upgrade to a fixed software release, which can be found using the Cisco Software Checker.

Fixed Software

• Cisco considers any workarounds and mitigations (if applicable) to be temporary solutions until an upgrade to a fixed software release is available. To 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:

  1. Choose which advisories the tool will search-only this advisory, only advisories with a Critical or High Security Impact Rating (SIR), or all advisories.
  2. Choose the appropriate software.
  3. Choose the appropriate platform.
  4. 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.
  5. Click Check.

  
  

  Only this advisory All Critical and High advisories All advisories Cisco NX-OS Software Cisco NX-OS Software in ACI Mode Any Platform MDS 9000 Series Multilayer Switches Nexus 3000 Series Switches Nexus 5000 Series Switches Nexus 6000 Series Switches Nexus 7000 Series Switches 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 3000 Series Switches
  Cisco Nexus 7000 Series Switches
  Cisco Nexus 9000 Series Switches
  Cisco Nexus 9000 Series ACI-Mode Switches

  To determine the best release for Cisco UCS Software, see the Recommended Releases documents in the release notes for the device.

Exploitation and Public Announcements

• 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.

Source

• This vulnerability was found during the resolution of a Cisco Technical Assistance Center (TAC) support case.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-n9k-s1-rce-EH8dEtr

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2026-SEP-02

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