dbcve.org
Metamako Operating SystemOperating system · Arista

CVE-2021-28495

CRITICAL · 9.8 CVSS v3.1 Published 2021-09-09
Fix available
A fix is available. Upgrade to 0.32.0 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In Arista's MOS (Metamako Operating System) software which is supported on the 7130 product line, under certain conditions, user authentication can be bypassed when API access is enabled via the JSON-RPC APIs. This issue affects: Arista Metamako Operating System All releases in the MOS-0.1x train MOS-0.13 and post 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

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Arista MOS (Metamako Operating System) on the 7130 product line contains an authentication bypass vulnerability in the JSON-RPC API. When API access is enabled, certain conditions allow attackers to bypass user authentication entirely, gaining unauthorized access to the system without valid credentials.

MitigationUpgrade to a patched MOS version beyond the vulnerable releases (MOS-0.26.6, MOS-0.31.1, or MOS-0.3x train). As an interim compensating control, restrict access to the JSON-RPC API via network ACLs or disable API access if not required.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Metamako Operating SystemOperating system
Affected:>= 0.10.0, <= 0.13.0>= 0.20.0, <= 0.26.7>= 0.30.0, < 0.32.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Confirm you are running Arista MOS on a 7130 series device
    Check the device model and product type via 'show version' or similar command that displays hardware model information
    Affected if Device is not an Arista 7130 series running MOS
  2. Identify the installed MOS version
    Run the command to display the MOS version (typically 'show version' or 'show system information') and note the firmware version number
    Affected if Version falls within these ranges: 0.10.0 to 0.13.0, 0.20.0 to 0.26.7, or 0.30.0 to below 0.32.0
  3. Determine if the JSON-RPC API is enabled
    Examine the device configuration for API or JSON-RPC settings, typically via 'show running-config' or a dedicated API configuration command
    Affected if API access is enabled in the device configuration
  4. Check network exposure of the JSON-RPC API
    Review interface configurations and ACL policies to determine if the API service port is accessible from untrusted networks
    Affected if The API is reachable from network segments outside the trusted administrative network

You are affected if you have an Arista 7130 device running MOS versions 0.10.0-0.13.0, 0.20.0-0.26.7, or 0.30.0-0.31.x with the JSON-RPC API enabled and accessible.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 0.32.0 or later
Fixed in 0.32.0
Interim mitigation

Upgrade to a patched MOS version beyond the vulnerable releases (MOS-0.26.6, MOS-0.31.1, or MOS-0.3x train). As an interim compensating control, restrict access to the JSON-RPC API via network ACLs or disable API access if not required.

Recommended fix High confidence

MOS-0.14.0+ for 0.1x train; MOS-0.26.8+ for 0.2x train; MOS-0.32.0+ for 0.3x train

  1. 1. Identify the current MOS version by running 'show version' or checking the system management interface
  2. 2. Determine which MOS train (0.1x, 0.2x, or 0.3x) the current version belongs to
  3. 3. For MOS-0.1x train (versions 0.10.0-0.13.0): Upgrade to MOS-0.14.0 or later
  4. 4. For MOS-0.2x train (versions 0.20.0-0.26.7): Upgrade to MOS-0.26.8 or later
  5. 5. For MOS-0.3x train (versions 0.30.0-0.31.1): Upgrade to MOS-0.32.0 or later
  6. 6. Download the appropriate upgrade image from Arista's support portal (www.arista.com)
  7. 7. Follow standard Arista upgrade procedures: upload the image, verify integrity, reboot to apply
  8. 8. After upgrade, verify the fix by confirming the version and testing API authentication
Caveat Review Arista release notes for any between-version compatibility changes or migration requirements specific to your train

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Metamako Operating System Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,600.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2021-28495 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-28495 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data