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PatchSiren cyber security CVE debrief

CVE-2021-3506 Siemens CVE debrief

An out-of-bounds memory access vulnerability in the Linux kernel's f2fs filesystem module affects 26 Siemens SCALANCE and RUGGEDCOM industrial networking products. The flaw, located in fs/f2fs/node.c in kernel versions before 5.12.0-rc4, stems from a bounds check failure that allows local attackers to access out-of-bounds memory. This can result in system crashes or information disclosure from internal kernel memory. The vulnerability requires local access with low privileges, no user interaction, and poses a high threat to system availability. Siemens has released firmware updates to address this issue.

Vendor
Siemens
Product
RUGGEDCOM RM1224 LTE(4G) EU (6GK6108-4AM00-2BA2)
CVSS
HIGH 7.1
CISA KEV
Not listed in stored evidence
Original CVE published
2021-04-19
Original CVE updated
2026-09-01
Advisory published
2021-04-19
Advisory updated
2026-09-01

Who should care

Industrial control system operators, OT security teams, and network administrators managing Siemens SCALANCE or RUGGEDCOM infrastructure in manufacturing, energy, transportation, and critical infrastructure sectors. Organizations with remote access to industrial networks or shared local access environments face elevated risk.

Technical summary

The vulnerability exists in the Flash-Friendly File System (f2fs) node management code within the Linux kernel. A bounds check failure in fs/f2fs/node.c permits out-of-bounds memory reads when processing f2fs filesystem structures. The attack vector is local, requiring low privileges but no user interaction. Successful exploitation can cause denial of service through system crashes or leak sensitive kernel memory contents. The CVSS 3.1 vector AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H reflects local attack complexity with high impacts to confidentiality and availability. Siemens has addressed this in firmware version 8.2 across affected SCALANCE M804PB, M812-1, M816-1, M826-2, M874-2, M874-3, M876-3, M876-4, MUM853-1, MUM856-1, S615, and RUGGEDCOM RM1224 product lines.

Defensive priority

high

Recommended defensive actions

  • Apply vendor firmware updates to version 8.2 or later for all affected SCALANCE and RUGGEDCOM devices
  • Verify current firmware version through Siemens Industry Online Support portal
  • Implement network segmentation to limit local access to industrial control devices
  • Monitor for anomalous system crashes or unexpected reboots on affected devices
  • Review CISA ICS recommended practices for defense-in-depth strategies
  • Subscribe to Siemens ProductCERT security advisories for future vulnerability notifications

Evidence notes

CVE published 2024-11-12 per CISA CSAF advisory ICSA-24-319-06. Modified 2025-05-06. Advisory references Siemens SSA-354112 for original vendor disclosure. 26 affected products across SCALANCE M-800 family, RUGGEDCOM RM1224, and SCALANCE S615 lines identified in CSAF product tree.

Sources and references

Verified primary and authoritative sources

  • CVE-2021-3506 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2021-3506

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

  • CVE-2021-3506 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2021-3506

    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-24-319-06.json

    cisa_csaf

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/csaf/ssa-354112.json

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/html/ssa-354112.html

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/news-events/ics-advisories/icsa-24-319-06

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/uscert/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://us-cert.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.