CVE-2021-27434Network attack vector

Arbitrary file read via XML external entities

Published May 20, 2021 · Updated Aug 3, 2024

XML external entity injection in Unified Automation .NET Based OPC UA SDK 3.0.7 and earlier allows remote attackers to read local files. The SDK relies on affected .NET DTD parsing that resolves attacker-supplied external entity references against local file paths. Exposure requires an application built for .NET Framework 4.5.1 or earlier to process attacker-controlled XML; no code execution or file modification is reported.

CVSS severity7.2
High
EPSS probability1.74%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

XML external entity injection in Unified Automation .NET Based OPC UA SDK 3.0.7 and earlier allows remote attackers to read local files. The SDK relies on affected .NET DTD parsing that resolves attacker-supplied external entity references against local file paths. Exposure requires an application built for .NET Framework 4.5.1 or earlier to process attacker-controlled XML; no code execution or file modification is reported.

The record

CVE
CVE-2021-27434
Published
May 20, 2021
Updated
Aug 3, 2024
Vendor
Unified Automation GmbH
Product
.NET Based OPC UA Client & Server SDK (Bundle)
Classifications
CWE-200, T1005
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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=Unified Automation .NET based OPC UA Client/Server SDK Bundle: Versions V3.0.7 and prior (.NET 4.5, 4.0, and 3.5 Framework versions only)

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Unified Automation GmbH · .NET Based OPC UA Client & Server SDK (Bundle)version=Unified Automation .NET based OPC UA Client/Server SDK Bundle: Versions V3.0.7 and prior (.NET 4.5, 4.0, and 3.5 Framework versions only)

Published CVSS scores

7.2OPC FoundationCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:L

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-200Exposure of Sensitive Information to an Unauthorized Actor
T1005Data from Local System

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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