# CVE-2026-31563: Linux Kernel DoS in macb network driver via invalid IRQ context

Source: https://junglewise.ai/threats/cve-2026-31563-linux-kernel-dos-in-macb-network-driver-via-invalid-irq-context  
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-2026-31563 · Severity: high · CVSS 7.5 · Published 2026-04-24

A vulnerability exists in the Linux kernel's network driver for Cadence MACB Ethernet controllers, which are commonly used in embedded systems and industrial controllers like Siemens SIMATIC S7-1500. The issue involves improper handling of network memory buffers during high-traffic scenarios, which can lead to system instability or a crash. An exploit could result in a denial-of-service, disrupting network communications and operational availability.

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). Vendors: [Linux](https://junglewise.ai/threats/vendors/linux), [Siemens](https://junglewise.ai/threats/vendors/siemens).

## Quick answers

**Is CVE-2026-31563 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-31563 being exploited in the wild.

**How severe is CVE-2026-31563?** High severity, with a CVSS score of 7.5, published 24 April 2026.

**Which products and versions are affected?** Linux Kernel 7.0.0-rc4-next-20260319-yocto-standard-dirty; 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.

**Is there a fix for CVE-2026-31563?** A patch was published on 2026-03-21: Initial patch authored by Kevin Hao Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-31563 attacked?** It is attacked over the network, in an operating system.

**Am I affected by CVE-2026-31563?** Check whether you run Linux Kernel, Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP or Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP 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 is a kernel panic/instability issue in the macb network driver (drivers/net/ethernet/cadence/macb_main.c). It was introduced by a previous locking fix (commit 6bc8a5098bf4) that resulted in TX SKB freeing being performed with interrupts (IRQs) disabled. The driver incorrectly calls napi_consume_skb() in this context, which is not permitted and triggers a kernel warning/trace in __local_bh_enable_ip. An attacker can potentially trigger this condition via network traffic, leading to a Denial of Service (DoS). The fix replaces the invalid call with dev_consume_skb_any(), which is safe for use in any context.

## Affected products

- Linux Linux Kernel 7.0.0-rc4-next-20260319-yocto-standard-dirty
- 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

## Timeline

- 2026-03-21: patched: Initial patch authored by Kevin Hao
- 2026-04-24: advisory: CVE published to NVD
- 2026-07-14: other: Siemens product impact information added to advisory

## References

- [https://git.kernel.org/stable/c/647b8a2fe474474704110db6bd07f7a139e621eb](https://git.kernel.org/stable/c/647b8a2fe474474704110db6bd07f7a139e621eb)
- [https://git.kernel.org/stable/c/78c8b090a3d5c1689dc989861b0163180db2b3f8](https://git.kernel.org/stable/c/78c8b090a3d5c1689dc989861b0163180db2b3f8)
- [https://git.kernel.org/stable/c/92e7081f0c79d9073087e54bab745bb184192c2e](https://git.kernel.org/stable/c/92e7081f0c79d9073087e54bab745bb184192c2e)
- [https://git.kernel.org/stable/c/984350b37372f79f71d4f0a5264c640e40daf9ce](https://git.kernel.org/stable/c/984350b37372f79f71d4f0a5264c640e40daf9ce)
- [https://git.kernel.org/stable/c/ca4d05afb4683d685bb2c6fccae4386c478f524a](https://git.kernel.org/stable/c/ca4d05afb4683d685bb2c6fccae4386c478f524a)
- [https://git.kernel.org/stable/c/f4bc91398b579730284328322365afa77a9d568f](https://git.kernel.org/stable/c/f4bc91398b579730284328322365afa77a9d568f)
- [https://cert-portal.siemens.com/productcert/html/ssa-019113.html](https://cert-portal.siemens.com/productcert/html/ssa-019113.html)

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