Date: August 20th, 2021

Version: 1.0

Revision Date Changes
1.0 August 20th, 2021 Initial Release

The CVE-ID tracking this issue: CVE-2021-28497
CVSSv3.1 Base Score: 4.4 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L)


This advisory documents the impact of an internally found vulnerability in Arista's MOS (Metamako Operating System) software which is supported on the 7130 product line. Under certain conditions, the bash shell may be accessible to unprivileged users in situations where they should not have access.

This issue was discovered internally and Arista is not aware of any malicious uses of this issue in customer networks.

Vulnerability Assessment

Affected Software


  • All releases in the MOS-0.1x train
  • MOS-0.26.6 and below releases in the MOS-0.2x train
  • MOS-0.31.1 and below releases in the MOS-0.3x train

Affected Platforms

The following products are affected by this vulnerability:

  • Arista 7130 Systems running MOS

The following products are not affected:

  • Arista EOS-based products
  • Arista Converged Cloud Fabric and DANZ Monitoring Fabric (Formerly Big Switch Nodes for BCF and BMF)
  • Arista Wireless Access Points
  • CloudVision Wi-Fi (on-premise and cloud service delivery)
  • CloudVision Portal, virtual appliance or physical appliance
  • CloudVision as-a-Service
  • Awake Security Platform


To check the version of MOS running on the system, use the following commands

Switch#show version
Device: Metamako MetaConnect 96 with E-Series
SKU: DCS-7130-96E
Serial number: C96E-A7-36803-2

Software image version: 0.26.5

<output omitted for brevity>

In the above example, as the Switch is running 0.26.5, it is exposed to the vulnerability.


There is no mitigation available to address this vulnerability. For the final resolution, please refer to the next section which lists the details of the remediated software versions.


This vulnerability is being tracked by BUG567396. The recommended resolution is to upgrade to a remediated MOS version during a maintenance window.

This vulnerability has been fixed in the following MOS version:

  • MOS-0.26.7
  • MOS-0.32.0

A hotfix has been implemented as an extension, which can be downloaded from the following link. Note that in addition to patches for the vulnerability described in this security advisory 65, this hotfix also contains patches for vulnerabilities covered under security advisories 64 and 66.

The above hotfix is applicable to the following releases:

  • MOS-0.26.6 and below releases in the MOS-0.26.x train
  • MOS-0.31.1 and below releases in the MOS-0.3x train

To install the hotfix, follow these instructions:

  • Copy the RPM to the device and install as an application
  • App install instructions available on EOS Central here and also in Section 5.7 (Application Commands) of the user guide available on the release page.
  • Verification of install can be done by checking the syslogs or the applications list in the output of ‘show version’
  • The hotfix will remain installed until explicitly removed, though it will not have any effect on the remediated releases. To remove the application, run the command: ‘remove app mos-1818-2.0.0’ at the config prompt

For More Information

If you require further assistance, or if you have any further questions regarding this security notice, please contact the Arista Networks Technical Assistance Center (TAC) by one of the following methods:

Open a Service Request:

By email: This email address is being protected from spambots. You need JavaScript enabled to view it.

By telephone: 408-547-5502 ; 866-476-0000