PatchSiren cyber security CVE debrief

CVE-2025-21787 Siemens CVE debrief

CVE-2025-21787 is a MEDIUM severity vulnerability (CVSS 5.5) affecting the Siemens SIMATIC S7-1500 TM MFP GNU/Linux subsystem. The issue involves improper validation of TEAM_OPTION_TYPE_STRING, which could lead to a denial-of-service condition. The vulnerability requires local access with low privileges and no user interaction, making it exploitable by authenticated users with shell access to the GNU/Linux subsystem. No patch is currently available; Siemens and CISA recommend restricting interactive shell access to trusted personnel only and ensuring only applications from trusted sources are built and executed. The vulnerability was disclosed in CISA advisory ICSA-24-102-01 on April 9, 2024, with the advisory receiving multiple updates through September 2025 to include additional related CVEs.

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

Organizations operating Siemens SIMATIC S7-1500 TM MFP controllers in industrial environments, particularly those utilizing the GNU/Linux subsystem for custom applications. OT security teams, plant engineers, and asset owners in manufacturing, process control, and critical infrastructure sectors should prioritize access controls given the absence of a security patch.

Technical summary

The vulnerability exists in the GNU/Linux subsystem of the Siemens SIMATIC S7-1500 TM MFP industrial controller. Insufficient validation of TEAM_OPTION_TYPE_STRING parameters can be exploited by a locally authenticated attacker with low privileges to cause a denial-of-service condition. The attack requires no user interaction and has no confidentiality or integrity impact, but results in high availability impact. The CVSS 3.1 vector is AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

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 future Siemens security advisories for patch availability
Apply defense-in-depth strategies for industrial control systems per CISA guidance

Evidence notes

CVE published 2024-04-09 per CISA CSAF source ICSA-24-102-01. Advisory modified 2026-05-14. CVSS vector AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H indicates local attack vector with availability impact. No fix available per remediation data.

Official resources

2024-04-09