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CVE-2024-47706 Siemens CVE debrief

A use-after-free (UAF) vulnerability exists in the Linux kernel's Budget Fair Queueing (BFQ) I/O scheduler. The flaw occurs when I/O from a process traverses a merge chain of BFQ queues (bfqq), causing the code to incorrectly associate a bfqq with a Block I/O Context (BIC) that no longer owns it. Specifically, when Process 1 obtains bfqq2 from BIC1, then acquires bfqq3 through a merge chain, the I/O is ultimately handled by bfqq3. However, the current code erroneously treats bfqq2 as still owned by BIC1 (as in its initial state) and sets bfqq2->bic to BIC1, leading to a use-after-free condition. This vulnerability was resolved in the Linux kernel. The issue affects Siemens SIMATIC S7-1500 TM MFP devices that utilize the GNU/Linux subsystem.

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
2025-08-12
Original CVE updated
2026-02-25
Advisory published
2025-08-12
Advisory updated
2026-02-25

Who should care

Organizations operating Siemens SIMATIC S7-1500 TM MFP programmable controllers with the GNU/Linux subsystem enabled, particularly in industrial automation and critical infrastructure environments where system availability is paramount. Security teams responsible for OT/ICS asset protection and patch management should prioritize monitoring for vendor updates.

Technical summary

The vulnerability resides in the block layer BFQ (Budget Fair Queueing) I/O scheduler of the Linux kernel. When I/O requests traverse a merge chain of BFQ queues, the scheduler fails to properly track ownership transitions between Block I/O Contexts (BICs) and their associated queue structures (bfqq). After a merge chain operation where bfqq2 is obtained from BIC1 and then bfqq3 is acquired through merging, the I/O is handled by bfqq3, but the code incorrectly maintains bfqq2->bic pointing to BIC1. This stale pointer reference creates a use-after-free condition when the BIC or queue structure is subsequently freed. The KASAN instrumentation trace confirms allocation through kmem_cache_alloc_node in the ioc_create_icq path, indicating the slab-allocated nature of the affected structures.

Defensive priority

medium

Recommended defensive actions

  • Apply vendor-provided firmware updates for Siemens SIMATIC S7-1500 TM MFP when available, per Siemens security advisory SSA-265688
  • Restrict interactive shell access to the GNU/Linux subsystem to trusted personnel only
  • Build and execute only applications from trusted sources on affected devices
  • Monitor for anomalous I/O scheduler behavior or system instability that may indicate exploitation attempts
  • Implement defense-in-depth strategies for industrial control systems per CISA recommended practices

Evidence notes

The vulnerability description is derived from the official CVE record and CISA CSAF advisory ICSA-24-102-01. The KASAN stack trace indicates memory allocation via kmem_cache_alloc_node in ioc_create_icq, confirming the slab allocation context for the affected BIC structures. The CVSS 3.1 vector AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H indicates local attack vector with low attack complexity, low privileges required, and high availability impact.

Sources and references

Verified primary and authoritative sources

  • CVE-2024-47706 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2024-47706

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2024-47706 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2024-47706

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Source item URL

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/cisagov/CSAF/develop/csaf_files/OT/white/2024/icsa-24-102-01.json

    cisa_csaf

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/csaf/ssa-265688.json

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/html/ssa-265688.html

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/news-events/ics-advisories/icsa-24-102-01

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/news-events/ics-alerts/ics-alert-10-301-01

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/resources-tools/resources/ics-recommended-practices

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/topics/industrial-control-systems

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/sites/default/files/recommended_practices/NCCIC_ICS-CERT_Defense_in_Depth_2016_S508C.pdf

    Reference

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.