PatchSiren cyber security CVE debrief

CVE-2025-21814 Siemens CVE debrief

A vulnerability in the Linux kernel's PTP (Precision Time Protocol) subsystem affects the GNU/Linux subsystem of Siemens SIMATIC S7-1500 TM MFP industrial controllers. The issue stems from a missing validation that the `info->enable` callback is set before invocation, which can lead to a NULL pointer dereference. This local vulnerability requires low privileges to exploit and results in high availability impact (system crash/denial of service). The vulnerability was disclosed in CISA advisory ICSA-24-102-01 on April 9, 2024, with subsequent updates through September 2025 adding related CVEs. No patch is currently available from the vendor.

Vendor: Siemens
Product: SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
CVSS: MEDIUM 5.5
CISA KEV: Not listed in stored evidence
Original CVE published: 2024-04-09
Original CVE updated: 2026-05-14
Advisory published: 2024-04-09
Advisory updated: 2026-05-14

Who should care

Operators of Siemens SIMATIC S7-1500 TM MFP industrial control systems, OT security teams, and infrastructure owners in manufacturing, energy, and critical infrastructure sectors using this PLC platform should prioritize access controls until a patch is available.

Technical summary

The vulnerability exists in the Linux kernel PTP (Precision Time Protocol) driver where the `info->enable` callback may not be validated as set before invocation. This can result in a NULL pointer dereference when the callback is called on an uninitialized or improperly configured PTP clock device. The flaw requires local access with low privileges to trigger, making it primarily a denial-of-service concern rather than a remote code execution vector. The affected product is the GNU/Linux subsystem within Siemens SIMATIC S7-1500 TM MFP programmable logic controllers, which embed a Linux-based environment for additional application hosting alongside the primary PLC runtime.

Defensive priority

medium

Recommended defensive actions

Restrict interactive shell access to the GNU/Linux subsystem to trusted personnel only
Only build and run applications from trusted sources
Monitor for anomalous local process activity on affected devices
Apply vendor patches when released per Siemens security advisory SSA-265688
Implement network segmentation for industrial control systems per CISA ICS recommended practices

Evidence notes

CVE published 2024-04-09 per CISA CSAF advisory ICSA-24-102-01. Advisory subsequently updated 10 times through 2025-09-09 to add related CVEs. CVSS 5.5 (MEDIUM) with vector AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H indicates local attack vector with low privileges required, no confidentiality or integrity impact, high availability impact. CWE-476 (NULL Pointer Dereference) classification per source references.

Official resources

2024-04-09