CVE-2020-29457

Rogue secure connection via suppressed certificate errors

Published Feb 16, 2021 · Updated Aug 4, 2024

Certificate validation bypass in OPC UA .NET Standard Stack 1.4.365.2 and earlier allows local users to connect using invalid certificates. CertificateValidator emits only the first chain failure, allowing suppression of that error to conceal later unsuppressible certificate defects. Exploitation requires certificate-error suppression and write access to the server trust list; the rogue application then receives a secure session.

CVSS severity4.4
Medium
EPSS probability0.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Certificate validation bypass in OPC UA .NET Standard Stack 1.4.365.2 and earlier allows local users to connect using invalid certificates. CertificateValidator emits only the first chain failure, allowing suppression of that error to conceal later unsuppressible certificate defects. Exploitation requires certificate-error suppression and write access to the server trust list; the rogue application then receives a secure session.

The record

CVE
CVE-2020-29457
Published
Feb 16, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-295, T1553.004
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Feb 16, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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 vectorlocal
Required privilegesadmin

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.4NIST NVDCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N

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)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-295Improper Certificate Validation
T1553.004Subvert Trust Controls: Install Root Certificate

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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