CVE-2026-35225Network attack vector

Denial of service via missing TCP timeouts

Published Apr 23, 2026 · Updated Apr 23, 2026

Denial of service in CODESYS EtherNet/IP before 4.9.0.0 allows remote attackers to block new TCP connections to configured adapters. The adapter stack omits timeout checks on active TCP connections, so expired connections remain allocated after the connection pool fills. Only projects with an EtherNet/IP adapter configuration are exposed; no authentication is required, and existing connections remain operational.

CVSS severity7.5
High
EPSS probability0.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in CODESYS EtherNet/IP before 4.9.0.0 allows remote attackers to block new TCP connections to configured adapters. The adapter stack omits timeout checks on active TCP connections, so expired connections remain allocated after the connection pool fills. Only projects with an EtherNet/IP adapter configuration are exposed; no authentication is required, and existing connections remain operational.

The record

CVE
CVE-2026-35225
Published
Apr 23, 2026
Updated
Apr 23, 2026
Vendor
CODESYS GmbH
Product
CODESYS EtherNet/IP
Classifications
CWE-754, T1499.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 23, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 23, 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=1.0.0.0 <4.9.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

CODESYS GmbH · CODESYS EtherNet/IPversion=1.0.0.0 <4.9.0.0

Published CVSS scores

7.5CERT@VDECVSS:3.1/AV:N/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.

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-754Improper Check for Unusual or Exceptional Conditions
T1499.002Endpoint Denial of Service: Service Exhaustion Flood

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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