PatchSiren cyber security CVE debrief

CVE-2024-26958 Siemens CVE debrief

A use-after-free (UAF) vulnerability in the Linux kernel's NFS direct write path was resolved in the upstream kernel. The vulnerability affects Siemens SIMATIC S7-1500 TM MFP industrial control systems that utilize the GNU/Linux subsystem. The flaw occurs during NFS direct write operations where improper memory management could lead to memory corruption. With a CVSS 3.1 score of 7.8 (HIGH), this local vulnerability requires low attack complexity and low privileges but can result in complete confidentiality, integrity, and availability compromise. The vulnerability was published on April 9, 2024, and the advisory has been updated multiple times through September 2025 to include additional related CVEs. Siemens has not released a patch for this specific product; mitigation relies on restricting access to trusted personnel and ensuring only trusted applications are executed.

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

Industrial control system operators, OT security teams, and asset owners deploying Siemens SIMATIC S7-1500 TM MFP controllers with activated GNU/Linux subsystems. Organizations in critical infrastructure sectors (energy, manufacturing, water/wastewater) utilizing these controllers for process automation should prioritize access restrictions and monitoring. Security teams responsible for patch management in air-gapped or long-lifecycle OT environments where kernel updates may be delayed. Compliance officers tracking CISA ICS advisories and Siemens ProductCERT notifications for vulnerability disclosure obligations.

Technical summary

The vulnerability exists in the Linux kernel's NFS (Network File System) implementation, specifically in the direct write code path. During direct I/O operations to NFS mounts, improper synchronization or reference counting can lead to a use-after-free condition where memory is accessed after being freed. This memory corruption vulnerability is exploitable locally with low privileges, enabling an attacker to potentially escalate privileges or cause system instability. The affected product is the GNU/Linux subsystem within Siemens SIMATIC S7-1500 TM MFP programmable logic controllers, which incorporate a Linux-based environment for extended functionality. While the upstream Linux kernel has resolved this issue, Siemens has not issued a product-specific patch, leaving affected systems dependent on access controls and trusted application policies for protection.

Defensive priority

HIGH

Recommended defensive actions

Restrict interactive shell access to the GNU/Linux subsystem to trusted personnel only
Ensure only applications from trusted sources are built and executed on affected systems
Monitor for anomalous NFS direct write operations or unexpected process behavior
Apply defense-in-depth strategies per CISA ICS recommended practices
Subscribe to Siemens ProductCERT security advisories for future patch availability

Evidence notes

Vulnerability description and resolution confirmed in CISA ICS advisory ICSA-24-102-01. CVSS vector AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H indicates local attack vector with high impact. Siemens CSAF document SSA-265688 provides vendor-specific context. Advisory revision history shows ongoing updates through September 2025, with the most recent update (Additional Release 9) adding 51 CVEs on September 9, 2025.

Official resources

2024-04-09