Beckhoff: Privilege Escalation through TwinCat System

published 2020-11-19 5y ago modified 2026-06-17 4mo ago also EUVD-2020-4812

cvss: 7.3; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.9%; EPSS 0.9% chance of exploitation in 30 days, percentile 59%
public exploits: 0; none known

The default installation path of the TwinCAT XAR 3.1 software in all versions is underneath C:\TwinCAT. If the directory does not exist it and further subdirectories are created with permissions which allow every local user to modify the content. The default installation registers TcSysUI.exe for automatic execution upon log in of a user. If a less privileged user has a local account he or she can replace TcSysUI.exe. It will be executed automatically by another user during login. This is also true for users with administrative access. Consequently, a less privileged user can trick a higher privileged user into executing code he or she modified this way. By default Beckhoff’s IPCs are shipped with TwinCAT software installed this way and with just a single local user configured. Thus the vulnerability exists if further less privileged users have been added.

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Exploit prediction

0.88% chance of exploitation in the next 30 days, higher than 59% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
CNA	3.1	7.3	CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
NVD	3.1	7.3	CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
NVD	2.0	6.0	AV:N/AC:M/Au:S/C:P/I:P/A:P

Affected products

Beckhoff TwinCat XAR 3.1

Classification

Weakness

CWE-276 Incorrect Default Permissions

References

cert.vde.com /en-us/advisories/vde-2020-037
third-party-advisory

Sources

CVE List CVE-2020-12510
NVD CVE-2020-12510

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