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CVE-2025-21727 Siemens CVE debrief

A use-after-free (UAF) vulnerability exists in the Linux kernel's padata subsystem, specifically within the `padata_reorder` function. The padata subsystem provides parallel data processing capabilities, and the flaw arises from improper memory management during reordering operations. A local attacker with low privileges can exploit this vulnerability to achieve privilege escalation, potentially gaining full control over the affected system. The vulnerability is classified as CWE-416 (Use After Free) and carries a CVSS 3.1 score of 7.8 (HIGH severity), with local attack vector, low attack complexity, and high impacts on confidentiality, integrity, and availability.

Vendor
Siemens
Product
SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
CVSS
HIGH 7.8
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 industrial control systems with the GNU/Linux subsystem enabled should prioritize this vulnerability. System administrators, OT security teams, and industrial control system operators in manufacturing, energy, and critical infrastructure sectors are particularly affected. The absence of an available patch necessitates immediate implementation of compensating controls.

Technical summary

The vulnerability exists in the `padata_reorder` function of the Linux kernel's parallel data processing (padata) subsystem. The flaw is a use-after-free condition that occurs during reordering operations, allowing a local attacker with low privileges to corrupt memory and escalate privileges. The attack requires local access with low privileges, no user interaction, and has low attack complexity. Successful exploitation results in complete compromise of confidentiality, integrity, and availability on the affected system.

Defensive priority

HIGH

Recommended defensive actions

  • Restrict interactive shell access to the GNU/Linux subsystem to trusted personnel only
  • Implement application whitelisting to ensure only trusted applications are built and executed
  • Monitor for anomalous privilege escalation attempts on affected systems
  • Apply vendor patches immediately upon release when Siemens provides a fix
  • Segment affected industrial control systems from untrusted networks
  • Implement defense-in-depth strategies per CISA ICS recommended practices

Evidence notes

The vulnerability was disclosed in CISA ICS Advisory ICSA-24-102-01 on April 9, 2024, and affects the GNU/Linux subsystem within Siemens SIMATIC S7-1500 TM MFP industrial control systems. The advisory has undergone multiple revisions, with the most recent update on September 9, 2025, adding 51 additional CVEs to the cumulative security notice. The source advisory explicitly states that currently no fix is available for this vulnerability.

Official resources

2024-04-09