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.NET
.NET NuGet
Not in CISA KEV
HIGH severity

CVE-2023-27321 — OPCFoundation.NetStandard…

HIGH

CVE-2023-27321 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in OPCFoundation.NetStandard.Opc.Ua.Server. A fix is available for OPCFoundation.NetStandard.Opc.Ua.Server — see the affected versions and patch details below.

OPC Foundation UA .NET Standard ConditionRefresh Resource Exhaustion Denial-of-Service Vulnerability

Also known asGHSA-vpf7-r2fv-75m9
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 1, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2023-27321.

EPSS Exploitation Probability

via FIRST.org ↗
1.0%probability of exploitation in next 30 days
Lower Risk+0.01%
Lower risk than most CVEs64th percentile — riskier than 64% of all scored CVEsHighest risk
0.37%1.56%2.75%3.93%1.3%1.0%May 26Aug 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
.NETOPCFoundation.NetStandard.Opc.Ua.Server

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.

Description

OPC Foundation UA .NET Standard ConditionRefresh Resource Exhaustion Denial-of-Service Vulnerability. This vulnerability allows remote attackers to create a denial-of-service condition on affected installations of OPC Foundation UA .NET Standard. Authentication is not required to exploit this vulnerability.

The specific flaw exists within the handling of OPC UA ConditionRefresh requests. By sending a large number of requests, an attacker can consume all available resources on the server. An attacker can leverage this vulnerability to create a denial-of-service condition on the system. Was ZDI-CAN-20505.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
.NETNuGetOPCFoundation.NetStandard.Opc.Ua.Serverall versions1.4.371.86dotnet add package OPCFoundation.NetStandard.Opc.Ua.Server --version 1.4.371.86

Affected Products

1 product · 1 configurations
Application
ua-.netstandardopcfoundation
< 1.4.371.86
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for OPCFoundation.NetStandard.Opc.Ua.Server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update OPCFoundation.NetStandard.Opc.Ua.Server to 1.4.371.86 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-27321 is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

OPC Foundation UA .NET Standard ConditionRefresh Resource Exhaustion Denial-of-Service Vulnerability. This vulnerability allows remote attackers to create a denial-of-service condition on affected installations of OPC Foundation UA .NET Standard. Authentication is not required to exploit this vulnerability. The specific flaw exists within the handling of OPC UA ConditionRefresh requests. By sending a large number of requests, an attacker can consume all available resources on the server. An attacker can leverage this vulnerability to create a denial-of-service condition on the system. Was ZDI
O3 Security · Impact-Aware SCA

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CVE-2023-27321: OPCFoundation — Fixed in 1.4.371.86