CVE-2024-43856 Siemens CVE debrief

Who should care

Industrial control system operators, OT security teams, and Linux kernel maintainers should prioritize this vulnerability. The affected Siemens SIMATIC S7-1500 TM MFP is deployed in manufacturing and critical infrastructure environments. System administrators responsible for embedded Linux systems using managed DMA coherent allocations should review their kernel versions. Security teams monitoring for kernel anomalies should watch for dmam_match WARN_ON() triggers as potential exploitation indicators.

Technical summary

The dmam_free_coherent() function in the Linux kernel's device resource management (devres) subsystem contains a race condition due to incorrect operation ordering. The function first calls dma_free_coherent() to release the DMA allocation, making the virtual address available for reuse, then subsequently calls devres_destroy() to remove the tracking structure. Between these two operations, a concurrent allocation may acquire the same virtual address and register it with devres, creating duplicate entries. The devres_destroy() call then matches and potentially frees the wrong entry based on virtual address comparison, triggering WARN_ON() in dmam_match(). The fix reverses this order: devres_destroy() is called first while the allocation remains valid and uniquely identifiable, then dma_free_coherent() releases the memory. This ensures atomicity from the perspective of the devres list. The vulnerability requires local access and low privileges, with exploitation resulting in denial of service through kernel warning storms or potential memory management corruption.

Defensive priority

medium

Recommended defensive actions

• Apply vendor-provided firmware updates for Siemens SIMATIC S7-1500 TM MFP when available, per advisory guidance
• 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 on affected systems
• Monitor for kernel WARN_ON() messages in dmam_match as potential indicators of exploitation attempts
• Review and apply CISA ICS recommended practices for defense-in-depth strategies
• Segment industrial control networks to limit lateral movement opportunities
• resourceLinkAnnotations: [ref-4, ref-5, ref-6, ref-8, ref-9, ref-10]

Evidence notes

The vulnerability description is sourced from CISA ICS Advisory ICSA-24-102-01, which references the upstream Linux kernel fix. The CVSS vector (AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H) indicates local exploitation with high availability impact. The affected product is confirmed as Siemens SIMATIC S7-1500 TM MFP GNU/Linux subsystem per CSAF product tree data.

Official resources