dbcve.org
EosOperating system · Arista

CVE-2021-28506

CRITICAL · 9.1 CVSS v3.1 Published 2022-01-14
Fix available
A fix is available. Upgrade to after 4.26.2f or later.
See remediation →
100/100
Remediation priority · Urgent
Public exploit Remotely reachable No privileges Zero-click Patch available

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
An issue has recently been discovered in Arista EOS where certain gNOI APIs incorrectly skip authorization and authentication which could potentially allow a factory reset of the device.

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
How this class of weakness works · CWE-285

The application confirms who you are but does not properly check whether you are permitted to perform a given action, so authenticated users reach functions or data meant for others. Attackers test roles and object references to find the gap. Remediation is an authorization check on every request, evaluated against the acting user's actual permissions.

General guidance for the improper authorization class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

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
EosOperating system
Affected:>= 4.24.0, <= 4.24.7m>= 4.25.0, <= 4.25.3>= 4.25.4, <= 4.25.4m>= 4.25.5, <= 4.25.5.1m>= 4.26.0, <= 4.26.2f

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
None
Integrity
High
Availability
High

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

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 a release after 4.26.2f
Vendor patch www.arista.com →
Recommended fix High confidence

EOS 4.24.8+ or EOS 4.25.6+ (depending on your branch)

  1. Identify your current EOS version using 'show version' command
  2. Determine which version branch you are running (4.24.x or 4.25.x)
  3. For EOS 4.24.x: upgrade to EOS 4.24.8 or later
  4. For EOS 4.25.0-4.25.3: upgrade to EOS 4.25.4 or later
  5. For EOS 4.25.4-4.25.4m: upgrade to EOS 4.25.5 or later
  6. For EOS 4.25.5-4.25.5.1m: upgrade to EOS 4.25.6 or later
  7. After upgrade, verify the gNOI authentication is properly enforced
  8. Consult Arista EOS release notes for any known migration issues
Caveat Review Arista release notes for your target version for any behavioral changes; upgrade within same major.minor branch first to minimize risk

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

We can identify the exact fixed release, upgrade, and verify it in staging — typical engagement from $2,300. Get the upgrade done

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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-2021-28506 in production — separate from our analysis above.

No notes yet

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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