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PatchSiren cyber security CVE debrief

CVE-2021-44879 Siemens CVE debrief

CVE-2021-44879 is a NULL pointer dereference vulnerability in the Linux kernel's F2FS (Flash-Friendly File System) garbage collection code. The flaw exists in the `gc_data_segment` function in `fs/f2fs/gc.c` where special files are not properly considered, leading to a `move_data_page` NULL pointer dereference. This vulnerability affects Linux kernel versions before 5.16.3. The issue was originally identified in the upstream Linux kernel and has been subsequently identified as affecting certain Siemens industrial networking products that incorporate vulnerable kernel versions, specifically the RUGGEDCOM RST2428P and SCALANCE X-family switches running SINEC OS. The vulnerability was published in CISA's ICS advisory ICSA-25-226-15 on August 12, 2025, with subsequent updates through February 25, 2026, reflecting ongoing coordination between CISA and Siemens ProductCERT. The advisory's threat assessment categorizes the impact as 'Misinformed' for the affected Siemens products, suggesting the actual risk posture may differ from initial assessments. Organizations operating affected Siemens industrial networking equipment should consult the vendor's security advisory for specific patch availability and apply kernel updates to versions 5.16.3 or later where applicable.

Vendor
Siemens
Product
RUGGEDCOM RST2428P (6GK6242-6PA00)
CVSS
Unknown
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 industrial networking infrastructure, particularly RUGGEDCOM RST2428P switches and SCALANCE XC-300/XR-300/XC-400/XR-500WG/XR-500 family devices. OT security teams responsible for patch management in industrial environments. System integrators and operators of critical infrastructure relying on Siemens SINEC OS-based networking equipment.

Technical summary

The vulnerability resides in the F2FS (Flash-Friendly File System) implementation within the Linux kernel. Specifically, the `gc_data_segment` function in `fs/f2fs/gc.c` fails to account for special files during garbage collection operations. This omission can trigger a NULL pointer dereference in the `move_data_page` function. The flaw was remediated in Linux kernel version 5.16.3. Siemens has identified this upstream vulnerability as affecting certain industrial networking products in their RUGGEDCOM RST2428P and SCALANCE X-family product lines that utilize affected kernel versions within SINEC OS. The CISA advisory's 'Misinformed' threat categorization suggests that the practical exploitability or impact may be limited or that initial risk assessments required correction, as evidenced by the advisory's revision history which included corrections to affected product lists.

Defensive priority

medium

Recommended defensive actions

  • Review CISA ICS advisory ICSA-25-226-15 and Siemens ProductCERT advisory SSA-613116 for affected product versions and patch status
  • Verify kernel version on affected Siemens RUGGEDCOM and SCALANCE devices running SINEC OS
  • Apply vendor-provided firmware updates that incorporate Linux kernel 5.16.3 or later
  • For systems where patching is not immediately feasible, implement network segmentation to limit exposure of affected industrial control devices
  • Monitor vendor security advisories for additional affected products or updated remediation guidance

Evidence notes

Vulnerability description sourced from CISA CSAF advisory ICSA-25-226-15, which references the upstream Linux kernel vulnerability in F2FS garbage collection code. The advisory was initially published August 12, 2025, and most recently updated February 25, 2026, based on Siemens ProductCERT SSA-613116. The threat category 'Misinformed' is explicitly noted in the source advisory for affected product IDs CSAFPID-0001, CSAFPID-0003, and CSAFPID-0004.

Official resources

2025-08-12