CVE-2025-40939

Name: CVE-2025-40939
Creator: NVD / NIST
Published: 2025-12-09T16:17:47.617+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.1/10EPSS 0.18%

Last modified Jun 17, 2026

CVE-2025-40939 is a medium-severity vulnerability rated 5.1/10 on the CVSS scale. A vulnerability has been identified in SIMATIC CN 4100 (All versions < V4.0.1). The affected device contains a USB port which allows unauthenticated connections. EPSS estimates a 0.18% chance of exploitation in the next 30 days.

Description

A vulnerability has been identified in SIMATIC CN 4100 (All versions < V4.0.1). The affected device contains a USB port which allows unauthenticated connections. This could allow an attacker with physical access to the device to trigger reboot that could cause denial of service condition.

Metrics

CVSS 3.1

4.6/10

CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS 4.0

5.1/10

CVSS:4.0/AV:P/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability

0.18%

7.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-284

Affected Software

Vendor	Product	Versions
Siemens	Simatic Cn 4100 Firmware	< 4.0.1

References

https://cert-portal.siemens.com/productcert/html/ssa-416652.htmlVendor Advisory

Timeline

Published: Dec 9, 2025
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2025-40939?

How severe is CVE-2025-40939?

CVE-2025-40939 has a CVSS score of 5.1/10 (MEDIUM severity). The EPSS model estimates a 0.18% probability of exploitation in the next 30 days.

How do I fix CVE-2025-40939?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2025-40939?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST