CVE-2026-31670: Linux Kernel memory exhaustion in rfkill subsystem

CVE-2026-31670 · Severity: medium · CVSS 5.5 · Published 2026-04-24

A vulnerability in the Linux kernel's radio frequency (rfkill) subsystem allows a local user to trigger an unlimited number of system events without processing them. This can lead to the system running out of memory, potentially causing a complete system crash or denial of service. This affects various Linux-based systems, including specific industrial controllers from Siemens.

Technologies: Linux Kernel, Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP, Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP, Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP. Vendors: Linux, Siemens.

Quick answers

Is CVE-2026-31670 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-31670 being exploited in the wild.
How severe is CVE-2026-31670?
Medium severity, with a CVSS score of 5.5, published 24 April 2026.
Which products and versions are affected?
Linux Kernel All versions prior to fix (e.g., fixed in 6.1.x, 6.6.x, 7.x); Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5, V3.1.6; Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP V3.1.5, V3.1.6; Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP V3.1.5, V3.1.6.
Is there a fix for CVE-2026-31670?
A patch was published on 2026-04-12: Initial patch authored by Greg Kroah-Hartman Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-31670 attacked?
It is attacked with local access, in an operating system.
Am I affected by CVE-2026-31670?
Check whether you run Linux Kernel, Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP, Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The vulnerability exists in 'net/rfkill/core.c' where the kernel does not bound the number of 'rfkill_int_event' structures that can be queued for a single file descriptor. A local userspace process can open an rfkill file descriptor and trigger a large volume of events without reading them, leading to kernel memory exhaustion. The fix introduces a hard limit (MAX_RFKILL_EVENT = 1000) on the number of pending events per data source. Exploitation requires local access but no special privileges beyond the ability to interact with rfkill devices.

Affected products

  • Linux Linux Kernel All versions prior to fix (e.g., fixed in 6.1.x, 6.6.x, 7.x)
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5, V3.1.6
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP V3.1.5, V3.1.6
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP V3.1.5, V3.1.6

Timeline

  • 2026-04-12: patched: Initial patch authored by Greg Kroah-Hartman
  • 2026-04-24: advisory: CVE published to NVD

References

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