No exploitation reported

CVE-2021-27434

No exploitation reported by the sources we read.

Published2021-05-20
WeaknessCWE-200 · CWE-674

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC

2021-05-2014:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-27434?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-27434?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Unified-automation .net based opc ua client\/server sdkversion to verify

Branch	Affected	Fixed in	Source
3.0	≤ 3.0.7	no fix published	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Vendor advisories

ICSA-21-133-04 CISA1 known affected
OPC UA Products Built with the .NET Framework 4.5, 4.0, and 3.5
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)

Full record on NVD

Fix

Mitigation from the vendor CISA ICSA-21-133-04 · 1 productUnified Automation has released software (login required) to address the .NET Framework vulnerabilities. OPC Foundation recommends users deploying OPC UA .NET products built against the .NET 4.5, 4.0, and 3.5 Frameworks should contact the product supplier to determine if an update is needed. Users …

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVSS 3.17.5read 2026-10-23
NVDCVSS 2.05read 2026-10-23
CNAweakness (CWE)CWE-200read 2026-10-23
NVDweakness (CWE)CWE-674read 2026-10-23
FIRST EPSSEPSS score1.7 %2026-10-22

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Published: 2021-05-20
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-27434?

Is CVE-2021-27434 actively exploited?

Active exploitation of CVE-2021-27434 has not been confirmed. Its EPSS score was 1.7% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-27434?

CVE-2021-27434 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.

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