CVE-2021-28503Network attack vector

Device access via skipped credential re-evaluation

Published Feb 4, 2022 · Updated Sep 16, 2024

Authentication bypass in Arista Networks Arista EOS allows remote attackers to access devices through eAPI with certificate authentication. The eAPI certificate-authentication path skips credential re-evaluation, allowing a certificate username to retain access when authorization should be rejected. Exploitation requires eAPI with an HTTPS SSL profile that trusts a user certificate; successful access permits commands within that username's effective authorization.

CVSS severity7.4
High
EPSS probability0.73%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Arista Networks Arista EOS allows remote attackers to access devices through eAPI with certificate authentication. The eAPI certificate-authentication path skips credential re-evaluation, allowing a certificate username to retain access when authorization should be rejected. Exploitation requires eAPI with an HTTPS SSL profile that trusts a user certificate; successful access permits commands within that username's effective authorization.

The record

CVE
CVE-2021-28503
Published
Feb 4, 2022
Updated
Sep 16, 2024
Vendor
Arista Networks
Product
Arista EOS
Classifications
CWE-305, CWE-287, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 4, 2022CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 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=EOS-4.23 <EOS-4.23.10
  2. Affected versionversion=EOS-4.24 <EOS-4.24.8
  3. Affected versionversion=EOS-4.25 <EOS-4.25.6
  4. Affected versionversion=EOS-4.26 <EOS-4.26.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Arista Networks · Arista EOSversion=EOS-4.23 <EOS-4.23.10; version=EOS-4.24 <EOS-4.24.8; version=EOS-4.25 <EOS-4.25.6; version=EOS-4.26 <EOS-4.26.3

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
7.4Arista NetworksCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-305Authentication Bypass by Primary Weakness
CWE-287Improper Authentication
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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