CVE-2026-51535Public exploitNetwork attack vector

Service interruption via blocking incomplete-packet read

Published Jul 8, 2026 · Updated Jul 8, 2026

Resource exhaustion in OpENer 2.3.0 allows remote attackers to interrupt EtherNet/IP service through an incomplete ENIP packet. HandleDataOnTcpSocket performs a blocking recv for the declared payload length inside the single-threaded NetworkHandlerProcessCyclic loop. An unauthenticated TCP client on port 44818 can hold one connection open after sending only the four-byte header, stalling all legitimate protocol requests until that connection closes or times out.

CVSS severity7.5
High
EPSS probability0.49%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in OpENer 2.3.0 allows remote attackers to interrupt EtherNet/IP service through an incomplete ENIP packet. HandleDataOnTcpSocket performs a blocking recv for the declared payload length inside the single-threaded NetworkHandlerProcessCyclic loop. An unauthenticated TCP client on port 44818 can hold one connection open after sending only the four-byte header, stalling all legitimate protocol requests until that connection closes or times out.

The record

CVE
CVE-2026-51535
Published
Jul 8, 2026
Updated
Jul 8, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 8, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5CISA-ADPCVSS: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.

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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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

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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