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CVE-2024-50035 Siemens CVE debrief

A use-of-uninitialized-value vulnerability exists in the Linux kernel's PPP (Point-to-Point Protocol) asynchronous framing implementation. The flaw occurs in ppp_async_encode() when processing empty socket buffers (skb) sent via PPPoE with zero-length payloads. An attacker with local access can trigger this condition to read uninitialized kernel memory, potentially exposing sensitive information or causing system instability. The vulnerability was discovered through syzbot fuzzing and affects the GNU/Linux subsystem of Siemens SIMATIC S7-1500 TM MFP industrial control systems.

Vendor
Siemens
Product
SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
CVSS
HIGH 7.1
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

Industrial control system operators, OT security teams, Siemens SIMATIC S7-1500 TM MFP administrators, Linux kernel maintainers for embedded/ICS environments, and organizations running PPPoE implementations on hardened Linux subsystems in critical infrastructure.

Technical summary

The vulnerability exists in ppp_async_encode() within drivers/net/ppp/ppp_async.c. When pppoe_sendmsg() is invoked with a zero-size payload, an empty socket buffer (skb) is created and passed through the PPP channel bridge to ppp_async_encode(). The function attempts to access skb data without proper validation of the buffer's content state, resulting in use of uninitialized slab memory. The call chain involves: pppoe_sendmsg() → release_sock() → __release_sock() → sk_backlog_rcv() → pppoe_rcv_core() → ppp_input() → ppp_channel_bridge_input() → ppp_async_send() → ppp_async_push() → ppp_async_encode(). The uninitialized memory is allocated via kmalloc_reserve() → kmem_cache_alloc_node_noprof() in the slab allocator.

Defensive priority

HIGH

Recommended defensive actions

  • Restrict interactive shell access to the GNU/Linux subsystem to trusted personnel only
  • Build and run only applications from trusted sources
  • Monitor for anomalous PPPoE traffic patterns indicating potential exploitation attempts
  • Apply kernel updates when Siemens releases patched firmware for the affected product
  • Implement network segmentation to limit exposure of industrial control system interfaces

Evidence notes

The vulnerability was reported by syzbot and resolved in the Linux kernel. The KMSAN (Kernel Memory Sanitizer) report confirms uninitialized memory access at ppp_async_encode() in drivers/net/ppp/ppp_async.c:545 when pppoe_sendmsg() is called with zero size, resulting in an empty skb being processed. The uninitialized memory originates from slab allocation in sock_wmalloc() during skb allocation.

Sources and references

Verified primary and authoritative sources

  • CVE-2024-50035 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2024-50035

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

  • CVE-2024-50035 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2024-50035

    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.