CVE-2026-19655

DHCP Relay restart via crafted Option 82 packet

Published Sep 15, 2026 · Updated Sep 15, 2026

Improper input validation in Arista EOS 4.35.5M and earlier allows remote attackers on a client-facing VLAN to restart DHCP Relay. Arista identifies the DHCP Relay service as the affected locus but does not disclose which Option 82 field or parsing operation mishandles the crafted packet. Exploitation requires DHCP relay, snooping, or server matching based on Option 82; the documented consequence is a relay-agent restart.

CVSS severity6.5
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Arista EOS 4.35.5M and earlier allows remote attackers on a client-facing VLAN to restart DHCP Relay. Arista identifies the DHCP Relay service as the affected locus but does not disclose which Option 82 field or parsing operation mishandles the crafted packet. Exploitation requires DHCP relay, snooping, or server matching based on Option 82; the documented consequence is a relay-agent restart.

The record

CVE
CVE-2026-19655
Published
Sep 15, 2026
Updated
Sep 15, 2026
Vendor
Arista Networks
Product
Arista EOS
Classifications
CWE-20, T1499.004
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=4.33.0 <=4.33.9M changes=[{"at":"4.33.10M","status":"unaffected"}]
  2. Affected versionversion=4.34.0 <=4.34.7.1M changes=[{"at":"4.34.8M","status":"unaffected"}]
  3. Affected versionversion=4.35.0 <=4.35.5M changes=[{"at":"4.35.6M","status":"unaffected"}]

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Arista Networks · Arista EOSversion=4.33.0 <=4.33.9M changes=[{"at":"4.33.10M","status":"unaffected"}]; version=4.34.0 <=4.34.7.1M changes=[{"at":"4.34.8M","status":"unaffected"}]; version=4.35.0 <=4.35.5M changes=[{"at":"4.35.6M","status":"unaffected"}]

Published CVSS scores

7.1Arista NetworksCVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
6.5Arista NetworksCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1499.004Application or System Exploitation

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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