CVE-2021-28494Network attack vector

Low-privilege Web UI authentication bypass

Published Sep 9, 2021 · Updated Aug 3, 2024

Improper authentication in Arista Networks MOS 0.34.0 and earlier allows remote authenticated users to bypass Web UI access controls. Arista has not published the affected Web UI component, triggering state, or incorrect authentication operation. The Web UI is enabled by default, and an unprivileged account is required; consequences are limited to unauthorized changes and service interruption.

CVSS severity9.6
Critical
EPSS probability0.88%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper authentication in Arista Networks MOS 0.34.0 and earlier allows remote authenticated users to bypass Web UI access controls. Arista has not published the affected Web UI component, triggering state, or incorrect authentication operation. The Web UI is enabled by default, and an unprivileged account is required; consequences are limited to unauthorized changes and service interruption.

The record

CVE
CVE-2021-28494
Published
Sep 9, 2021
Updated
Aug 3, 2024
Vendor
Arista Networks
Product
MOS (Metamako Operating System)
Classifications
CWE-287, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 9, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=MOS-0.35.0 <MOS-0.35.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Arista Networks · MOS (Metamako Operating System)version=MOS-0.35.0 <MOS-0.35.0

Published CVSS scores

6.5NIST NVDAV:N/AC:L/Au:S/C:P/I:P/A:P
9.6Arista Networks, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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