CVE-2021-27432Network attack vector

Service interruption via unbounded XML matrix recursion

Published May 20, 2021 · Updated Aug 3, 2024

Uncontrolled recursion in OPC Foundation UA .NET Standard before 1.4.365.48 and UA .NET Legacy allows remote attackers to trigger a stack overflow. The XmlDecoder.ReadMatrix and XmlEncoder.WriteMatrix methods recursively process XML matrices without enforcing the configured encoding-nesting limit. No authentication or user interaction is required; network reachability to an OPC UA server is sufficient to exhaust its call stack and interrupt service.

CVSS severity7.5
High
EPSS probability1.95%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled recursion in OPC Foundation UA .NET Standard before 1.4.365.48 and UA .NET Legacy allows remote attackers to trigger a stack overflow. The XmlDecoder.ReadMatrix and XmlEncoder.WriteMatrix methods recursively process XML matrices without enforcing the configured encoding-nesting limit. No authentication or user interaction is required; network reachability to an OPC UA server is sufficient to exhaust its call stack and interrupt service.

The record

CVE
CVE-2021-27432
Published
May 20, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-674, T1499
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?

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

7.5OPC 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.

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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-674Uncontrolled Recursion
T1499Endpoint Denial of Service

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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