CVE-2021-28500Network attack vector

Unauthenticated device access via flawed AAA authorization

Published Jan 14, 2022 · Updated Sep 16, 2024

Improper authorization in Arista EOS 4.26.1F and earlier allows remote attackers to gain unrestricted device access through OpenConfig. The OpenConfig agents call EOS AAA APIs incorrectly, treating a configured nopassword local account as authorized for unrestricted access over enabled gNMI, gNOI, or RESTCONF transports. Exploitation requires an enabled OpenConfig transport, disabled nopassword remote-login protection, and an existing nopassword local user; mutual TLS protects gNMI but not RESTCONF.

CVSS severity9.1
Critical
EPSS probability0.81%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper authorization in Arista EOS 4.26.1F and earlier allows remote attackers to gain unrestricted device access through OpenConfig. The OpenConfig agents call EOS AAA APIs incorrectly, treating a configured nopassword local account as authorized for unrestricted access over enabled gNMI, gNOI, or RESTCONF transports. Exploitation requires an enabled OpenConfig transport, disabled nopassword remote-login protection, and an existing nopassword local user; mutual TLS protects gNMI but not RESTCONF.

The record

CVE
CVE-2021-28500
Published
Jan 14, 2022
Updated
Sep 16, 2024
Vendor
Arista Networks
Product
Arista EOS
Classifications
CWE-285, T1078
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 14, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=4.20 <0
  2. Affected versionversion=4.21.14M <=4.21.0
  3. Affected versionversion=4.22.11M <=4.22.0
  4. Affected versionversion=4.23.8M <=4.23.0
  5. Affected versionversion=4.24.6M <=4.24.6.0
  6. Affected versionversion=4.25.4.M <=4.25.0
  7. Affected versionversion=4.26.1F <=4.26.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Arista Networks · Arista EOSversion=4.20 <0; version=4.21.14M <=4.21.0; version=4.22.11M <=4.22.0; version=4.23.8M <=4.23.0; version=4.24.6M <=4.24.6.0; version=4.25.4.M <=4.25.0; version=4.26.1F <=4.26.0

Published CVSS scores

6.9NIST NVDAV:L/AC:M/Au:N/C:C/I:C/A:C
9.1Arista Networks, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
7.8NIST NVDCVSS:3.1/AV:L/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.

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

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-285Improper Authorization
T1078Valid Accounts

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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