Summary

• A vulnerability in the CLI console login authentication of Cisco Nexus 9300-FX3 Series Fabric Extender (FEX) when used in UCS Fabric Interconnect deployments could allow an unauthenticated attacker with physical access to bypass authentication.

  This vulnerability is due to the improper implementation of the password validation function. An attacker could exploit this vulnerability by logging in to the console port on an affected device. A successful exploit could allow the attacker to bypass authentication and execute a limited set of commands local to the FEX, which could cause a device reboot and denial of service (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-elyfex-dos-gfvcByx

  This advisory is part of the February 2023 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 2023 Semiannual Cisco FXOS and NX-OS Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco Nexus 9300-FX3 Series FEX when used with the following Cisco products if they are running a vulnerable release of Cisco UCS Software:

  • UCS 6400 Series Fabric Interconnects
  • UCS 6500 Series Fabric Interconnects

  Only the following Cisco Nexus 9000 Series PIDs when configured in FEX mode are vulnerable: 
  

  • N9K-C93180YC-FX3
  • N9K-C93180YC-FX3S

  Note: These PIDs are not vulnerable if they are used in FEX mode with a Cisco Nexus 9000 parent switch or if they are configured as a standalone Top of Rack (TOR) switch.

  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 Cisco Nexus 9000 Series PID

  To verify the FEX PID in Intersight Management Mode (IMM), use the show fex command as shown in the following example:

  IMM:
  6500-FI# show fex
  FEX 23:
     Name: FEX0023
     Model: N9K-C93180YC-FX3
     Serial: FDO250.....
     State: Online
  

  To verify the FEX PID in UCSM Management Mode (UMM), use the show fex detail | grep PID command in the CLI as shown in the following example:

  UMM:
  6400-FI# show fex detail | grep PID
      PID: N9K-C93180YC-FX3

   

  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 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 3100 Series 
    
  • UCS 6200 Series Fabric Interconnects
    
  • UCS 6300 Series Fabric Interconnects

Workarounds

• There are no workarounds that address this vulnerability.

Fixed Software

• 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 UCS Software

  At the time of publication, the release information in the following table(s) was accurate. See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information.

  The left column lists Cisco software releases, and the right column indicates whether a release was affected by the vulnerability described in this advisory and which release included the fix for this vulnerability.

  Cisco UCS Software Release	First Fixed Release for This Vulnerability
  4.0	Not vulnerable1
  4.1	Not vulnerable1
  4.2	4.2(2d)

  1. The Nexus 9300-FX3 Series FEX is supported only with Cisco UCS Software release 4.2(1d) and later.

  The Cisco Product Security Incident Response Team (PSIRT) validates only the affected and fixed release information that is documented in this advisory.

Exploitation and Public Announcements

• The Cisco 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 internal security testing.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-elyfex-dos-gfvcByx

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	—	Final	2023-FEB-22

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