dbcve.org
EosOperating system · Arista

CVE-2021-28496

MEDIUM · 6.5 CVSS v3.1 Published 2021-10-21
Fix available
A fix is available. Upgrade to 4.23.10 / 4.24.8 or later.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable 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
On systems running Arista EOS and CloudEOS with the affected release version, when using shared secret profiles the password configured for use by BiDirectional Forwarding Detection (BFD) will be leaked when displaying output over eAPI or other JSON outputs to other authenticated users on the device. The affected EOS Versions are: all releases in 4.22.x train, 4.23.9 and below releases in the 4.23.x train, 4.24.7 and below releases in the 4.24.x train, 4.25.4 and below releases in the 4.25.x train, 4.26.1 and below releases in the 4.26.x 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

In Arista EOS with shared secret profiles for BiDirectional Forwarding Detection (BFD), the configured BFD password is inadvertently disclosed in eAPI and other JSON output to other authenticated users on the device, allowing unauthorized credential exposure.

MitigationUpgrade EOS to a version beyond the affected releases (4.23.x above 4.23.9, 4.24.x above 4.24.7, 4.25.x above 4.25.4, 4.26.x above 4.26.1, or 4.27+). If upgrade is not immediately feasible, limit access to eAPI and JSON outputs to only trusted administrators.

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
EosOperating system
Affected:>= 4.22, <= 4.22.7m>= 4.23, < 4.23.10>= 4.24, < 4.24.8>= 4.25, < 4.25.5>= 4.26, < 4.26.2

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

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

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. Check EOS version
    Run 'show version' or 'show version detail' to obtain the installed EOS version
    Affected if Version falls within >= 4.22, <= 4.22.7m; >= 4.23, < 4.23.10; >= 4.24, < 4.24.8; >= 4.25, < 4.25.5; or >= 4.26, < 4.26.2
  2. Verify BFD configuration with shared secret
    Run 'show running-config | grep -A 10 bfd' or 'show bfd neighbor' to check if BFD is configured with authentication (shared secret profiles)
    Affected if BFD is configured with shared secret profiles containing passwords
  3. Check if eAPI is enabled
    Run 'show management api http-commands' to verify if eAPI (management API) is enabled on the device
    Affected if eAPI is enabled and accessible to authenticated users

User is affected if running a vulnerable EOS version AND BFD shared secret profiles are configured AND eAPI or JSON output access is available to non-privileged authenticated users

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 4.23.10 / 4.24.8 / 4.25.5 or later
Fixed in 4.23.104.24.84.25.5
Interim mitigation

Upgrade EOS to a version beyond the affected releases (4.23.x above 4.23.9, 4.24.x above 4.24.7, 4.25.x above 4.25.4, 4.26.x above 4.26.1, or 4.27+). If upgrade is not immediately feasible, limit access to eAPI and JSON outputs to only trusted administrators.

Recommended fix High confidence

4.22.x -> 4.22.8 or later; 4.23.x -> 4.23.10; 4.24.x -> 4.24.8; 4.25.x -> 4.25.5

  1. Identify the current EOS version using 'show version' command
  2. Determine which version train (4.22.x, 4.23.x, 4.24.x, or 4.25.x) the device is running
  3. Upgrade to the fixed version for that train: 4.22.8+ for 4.22.x, 4.23.10 for 4.23.x, 4.24.8 for 4.24.x, or 4.25.5 for 4.25.x
  4. After upgrade, verify the fix by checking if BFD passwords are no longer exposed in 'show bfd neighbors detail' JSON output via eAPI
  5. Ensure only authorized administrators have access to eAPI/JSON outputs
Caveat Standard EOS upgrade considerations apply - review Arista release notes for compatibility with other deployed features

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

Fix this in Eos Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,408.

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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-2021-28496 in production — separate from our analysis above.

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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