Junglewise Threat Intelligence

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

CVE-2026-31563 · Severity: high · CVSS 7.5 · Published 2026-04-24

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

Executive brief

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.

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

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