CVE-2025-40939 Denial of service in SIMATIC CN 4100

What is CVE-2025-40939?

CVE-2025-40939 is a medium-severity denial of service vulnerability in Siemens SIMATIC CN 4100, published on 9 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.

Official 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.

Weakness: CWE-284

Which versions are affected by CVE-2025-40939?

It affects 1 product.

Products include Siemens Simatic Cn 4100 Firmware.

How do I fix CVE-2025-40939?

No fix has been published for CVE-2025-40939 yet. Limit exposure of the affected software until one is available.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2025-40939 being exploited?

There is no known exploitation of CVE-2025-40939 in the wild and no public exploit code.

Other vulnerabilities in Siemens SIMATIC CN 4100

• CVE-2024-32741 Hardcoded credentials in SIMATIC CN 4100 Critical 10.0
• CVE-2023-29130 Privilege escalation in SIMATIC CN 4100 Critical 9.9
• CVE-2024-32740 Hardcoded credentials in SIMATIC CN 4100 Critical 9.8
• CVE-2023-49621 Hardcoded credentials in SIMATIC CN 4100 Critical 9.8
• CVE-2025-40938 Hardcoded credentials in SIMATIC CN 4100 Critical 9.2

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-35wm-hq5r-2p36.