CVE-2021-27434
mediumpriority · track · 31EPSS 0.017 · 78 %ileDEEURUUSEPSS · scored 2026-10-27
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.
remediations
Vendor fix, mitigation, or workaround guidance, as published by each source.
A vendor fix is available.
- Fixedbeckhoff_psirt
Update to a recent version of the affected product and update the .NET Framework.
- Mitigationbeckhoff_psirt
Consider limiting access to the network communication ports of affected server products. Also consider limiting where the affected client products are allowed to connect to. For example, this can be achived with Windows' built-in firewall by incoming rules for servers and outgoing rules for clients. Consider to minimize the ability of an attacker to hijack communication establishment from a client to a server. For example this can be achieved with the help of zones and conduits: Try to keep servers and clients within the same network zone and prevent intrusion into that zone. Try to enclose communication establishment within conduits like VPN channels (where one conduit can serve for many OPC UA connections) and prevent attackers from intruding into such channels. Consider updating the .NET Framework.
- MitigationUnified Automation .NET based OPC UA Client/Server SDK Bundlecisa_csaf_ot
Unified 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 should also consider upgrading to a version of the product using .NET 4.5.2 Framework or later. It is recommended users avoid using the end-of-life version of the .NET Framework due to the risk of unpatched vulnerabilities.
https://www.unified-automation.com/downloads/opc-ua-development.html
cvss
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 5–7.5
weaknesses
The CWE weakness classes this flaw belongs to.
affected products (49)
Products and version ranges known to be affected.
advisories (2)
Vendor and ecosystem advisories describing this.
- VDE-2021-008Beckhoff: Stack Overflow and XXE vulnerability in various OPC UA products2024-10-21csaf · beckhoff_psirtDE
The affected products can act as OPC UA client or server and are vulnerable to two different kind of attacks via the OPC UA protocol. For both cases the attacker can send packets via the OPC UA protocol without the need to authenticate and 1. provoke a stack overflow resulting in denial of service of the product or 2. make the product disclose information to the attacker without authorization.
- ICSA-21-133-04OPC UA Products Built with the .NET Framework 4.5, 4.0, and 3.52021-05-13icsa · cisa_csaf_otUS
Successful exploitation of this vulnerability could allow an unauthenticated attacker to read any file on the file system.
also known as (6)
Other names and identifiers for this entity.
sources
Which sources assert this record, and when.
references (6)
External citations — patches, advisories, analysis.
- https://cert-portal.siemens.com/productcert/pdf/ssa-752103.pdfPatchcnnvd
- https://us-cert.cisa.gov/ics/advisories/icsa-21-133-04cnnvd
- https://www.auscert.org.au/bulletins/ESB-2021.1653cnnvd
- https://www.cybersecurity-help.cz/vdb/SB2021051404cnnvd
- https://us-cert.cisa.gov/ics/advisories/icsa-21-133-04enisa_euvd
- https://us-cert.cisa.gov/ics/advisories/icsa-21-133-04Third Party AdvisoryUS Government Resourcenvd
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