CVE-2026-73444

Gateway takeover via VRRPv2 authentication bypass

Published Sep 15, 2026 · Updated Sep 15, 2026

Authentication bypass in Arista EOS allows remote attackers on the same layer 2 segment to claim the VRRP virtual router master role. Arista has not disclosed the exact verification error in the VRRPv2 IP-AH authentication implementation. Exposure requires VRRPv2 IP-AH authentication on an interface; successful takeover enables interception, modification, or discarding of virtual-gateway traffic.

CVSS severity5.3
Medium
EPSS probability0.30%
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 EOS allows remote attackers on the same layer 2 segment to claim the VRRP virtual router master role. Arista has not disclosed the exact verification error in the VRRPv2 IP-AH authentication implementation. Exposure requires VRRPv2 IP-AH authentication on an interface; successful takeover enables interception, modification, or discarding of virtual-gateway traffic.

The record

CVE
CVE-2026-73444
Published
Sep 15, 2026
Updated
Sep 15, 2026
Vendor
Arista Networks
Product
Arista EOS
Classifications
CWE-303, T1557
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 15, 2026Record 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=0
  2. Affected versionversion=4.33.0 <=4.33.9M changes=[{"at":"4.33.10M","status":"unaffected"}]
  3. Affected versionversion=4.34.0 <=4.34.7M changes=[{"at":"4.34.8M","status":"unaffected"}]
  4. Affected versionversion=4.35.0 <=4.35.5M changes=[{"at":"4.35.6M","status":"unaffected"}]
  5. Affected versionversion=4.36.0 <=4.36.1F changes=[{"at":"4.36.2F","status":"unaffected"}]

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Arista Networks · Arista EOSversion=0; version=4.33.0 <=4.33.9M changes=[{"at":"4.33.10M","status":"unaffected"}]; version=4.34.0 <=4.34.7M changes=[{"at":"4.34.8M","status":"unaffected"}]; version=4.35.0 <=4.35.5M changes=[{"at":"4.35.6M","status":"unaffected"}]; version=4.36.0 <=4.36.1F changes=[{"at":"4.36.2F","status":"unaffected"}]

Published CVSS scores

5.3Arista NetworksCVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
4.7Arista NetworksCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L

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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-303Incorrect Implementation of Authentication Algorithm
T1557Adversary-in-the-Middle

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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