# CVE-2025-40939: A vulnerability has been identified in SIMATIC CN 4100 (All versions < V4.0.1). The affected device contains a USB…

Source: https://junglewise.ai/threats/cve-2025-40939-a-vulnerability-has-been-identified-in-simatic-cn-4100-all  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2025-12-09  
License: CC BY 4.0 with a link back

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.

Technologies: [Siemens SIMATIC CN 4100](https://junglewise.ai/threats/technologies/simatic-cn-4100), [Siemens Simatic Cn 4100 Firmware](https://junglewise.ai/threats/technologies/simatic-cn-4100-firmware). Vendors: [Siemens](https://junglewise.ai/threats/vendors/siemens).

## Quick answers

**Is CVE-2025-40939 exploited in the wild?** 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.

## Affected products

- Siemens SIMATIC CN 4100
- Siemens Simatic Cn 4100 Firmware

## Related threats

- [Siemens SIMATIC CN 4100 resource exhaustion via TCP SYN flood](https://junglewise.ai/threats/cve-2026-22925-siemens-simatic-cn-4100-resource-exhaustion-via-tcp-syn-flood)
- [Siemens SIMATIC CN 4100 missing authentication and resource exhaustion](https://junglewise.ai/threats/cve-2026-22924-siemens-simatic-cn-4100-missing-authentication-and-resource)
- [Linux Kernel crypto algif_aead improper memory handling](https://junglewise.ai/threats/cve-2026-31431-linux-kernel-crypto-algif-aead-improper-memory-handling)
- [OpenSSL uninitialized memory disclosure in RSASVE key encapsulation](https://junglewise.ai/threats/cve-2026-31790-openssl-uninitialized-memory-disclosure-in-rsasve-key)
- [OpenSSL heap buffer overflow in buf2hex conversion](https://junglewise.ai/threats/cve-2026-31789-openssl-heap-buffer-overflow-in-buf2hex-conversion)