CVE-2023-27321Network attack vector

Service interruption via unbounded ConditionRefresh allocations

Published May 7, 2024 · Updated Aug 2, 2024

Resource exhaustion in OPC Foundation OPC UA .NET Standard Reference Server 1.4.371.60 allows remote attackers to exhaust server memory. The server handles repeated ConditionRefresh requests by allocating memory for each request without enforcing an aggregate resource limit. Anonymous network access is sufficient; sustained requests consume all available memory and interrupt the reference server without affecting confidentiality or integrity.

CVSS severity7.5
High
EPSS probability1.05%
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 OPC Foundation OPC UA .NET Standard Reference Server 1.4.371.60 allows remote attackers to exhaust server memory. The server handles repeated ConditionRefresh requests by allocating memory for each request without enforcing an aggregate resource limit. Anonymous network access is sufficient; sustained requests consume all available memory and interrupt the reference server without affecting confidentiality or integrity.

The record

CVE
CVE-2023-27321
Published
May 7, 2024
Updated
Aug 2, 2024
Vendor
OPC Foundation
Product
OPC UA .NET Standard Stack
Classifications
CWE-1325, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 7, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 2, 2024Record 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=1.4.371.60

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OPC Foundation · OPC UA .NET Standard Stackversion=1.4.371.60

Published CVSS scores

7.5Zero Day InitiativeCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5OPC FoundationCVSS: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 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-1325Improperly Controlled Sequential Memory Allocation
T1499.003Application 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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