CVE-2025-40939: A vulnerability has been identified in SIMATIC CN 4100 (All versions < V4.0.1). The affected device contains a USB…
CVE-2025-40939 · Severity: medium · CVSS 4.6 · Published 2025-12-09
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.
No. Junglewise Threat Intelligence has no report of CVE-2025-40939 being exploited in the wild.
How severe is CVE-2025-40939?
Medium severity, with a CVSS score of 4.6, published 9 December 2025.
Which products and versions are affected?
Siemens SIMATIC CN 4100, Siemens Simatic Cn 4100 Firmware. The advisory does not name versions.
Is there a fix for CVE-2025-40939?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
Am I affected by CVE-2025-40939?
Check whether you run Siemens SIMATIC CN 4100 or Siemens Simatic Cn 4100 Firmware. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.