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

Source: https://junglewise.ai/threats/cve-2026-31670-linux-kernel-memory-exhaustion-in-rfkill-subsystem  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-24. Updated: 2026-07-14  
License: CC BY 4.0 with a link back

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](https://junglewise.ai/threats/technologies/kernel), [Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP](https://junglewise.ai/threats/technologies/simatic-s7-1500-cpu-1518-4-pn-dp-mfp), [Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP](https://junglewise.ai/threats/technologies/simatic-s7-1500-cpu-1518f-4-pn-dp-mfp), [Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP](https://junglewise.ai/threats/technologies/siplus-s7-1500-cpu-1518-4-pn-dp-mfp). Vendors: [Linux](https://junglewise.ai/threats/vendors/linux), [Siemens](https://junglewise.ai/threats/vendors/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

- [https://git.kernel.org/stable/c/4bcd1615a4e2a185ae9edd27b4143d7dfa7134f4](https://git.kernel.org/stable/c/4bcd1615a4e2a185ae9edd27b4143d7dfa7134f4)
- [https://git.kernel.org/stable/c/673d2a3eef6e0ee9736501a150c9e4024a4e60a6](https://git.kernel.org/stable/c/673d2a3eef6e0ee9736501a150c9e4024a4e60a6)
- [https://git.kernel.org/stable/c/80ce4cb026f0a4c4532b6cad827b44debda6256a](https://git.kernel.org/stable/c/80ce4cb026f0a4c4532b6cad827b44debda6256a)
- [https://git.kernel.org/stable/c/82843afc19012a29ba863961ef494165aa1a88f4](https://git.kernel.org/stable/c/82843afc19012a29ba863961ef494165aa1a88f4)
- [https://git.kernel.org/stable/c/a8c26800e0220e1550af012f5a20e50f5c78864d](https://git.kernel.org/stable/c/a8c26800e0220e1550af012f5a20e50f5c78864d)
- [https://git.kernel.org/stable/c/b1e0c8d3ab58a0161db487bf5fc47adfcaf5d5ca](https://git.kernel.org/stable/c/b1e0c8d3ab58a0161db487bf5fc47adfcaf5d5ca)
- [https://git.kernel.org/stable/c/e3842779547c83150569071d9980517cc9029fc0](https://git.kernel.org/stable/c/e3842779547c83150569071d9980517cc9029fc0)

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