How severe is CVE-2021-27434?

CVE-2021-27434 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2021-27434 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (75th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-27434?

CVE-2021-27434 affects Unified-automation .net Based Opc Ua Client/server Sdk. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-27434?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-27434 published?

CVE-2021-27434 was published on 2021-05-20 and last updated on 2026-06-17.

CVE-2021-27434

CVE-2021-27434 is a high-severity vulnerability in Unified-automation .net Based Opc Ua Client/server Sdk with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-674.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 2% (75th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-674
Affected product: Unified-automation .net Based Opc Ua Client/server Sdk
Published: 2021-05-20
Last modified: 2026-06-17

Description

Products with 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) are vulnerable to an uncontrolled recursion, which may allow an attacker to trigger a stack overflow.

Frequently asked questions

What is CVE-2021-27434?: Products with 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) are vulnerable to an uncontrolled recursion, which may allow an attacker to trigger a stack overflow.
How severe is CVE-2021-27434?: CVE-2021-27434 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2021-27434 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (75th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-27434?: CVE-2021-27434 affects Unified-automation .net Based Opc Ua Client/server Sdk. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-27434?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-27434 published?: CVE-2021-27434 was published on 2021-05-20 and last updated on 2026-06-17.

References

https://us-cert.cisa.gov/ics/advisories/icsa-21-133-04

Affected products (1)

cpe:2.3:a:unified-automation:.net_based_opc_ua_client\/server_sdk:*:*:*:*:*:*:*:*

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