CVE-2026-31752: Linux Kernel out-of-bounds read in bridge ND option parsing

CVE-2026-31752 · Severity: medium · CVSS 5.5 · Published 2026-05-01

A vulnerability was identified in the Linux kernel's network bridging component, which is also used in certain Siemens industrial controllers. An attacker could exploit this flaw to cause a system crash or denial-of-service by sending specially crafted network packets. This could disrupt industrial operations or corporate network connectivity depending on where the affected software is deployed.

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-2026-31752 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-31752 being exploited in the wild.
How severe is CVE-2026-31752?
Medium severity, with a CVSS score of 5.5, published 1 May 2026.
Which products and versions are affected?
Linux Kernel Fixed in 259466f, 82a42ec, 837392a, 8508379, c49b925, e0bfd6d, e71303a, ee02d89; 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-2026-31752?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-31752 attacked?
It is attacked with local access, in an operating system.
Am I affected by CVE-2026-31752?
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 the br_nd_send() function within net/bridge/br_arp_nd_proxy.c. The function iterates through Neighbor Discovery (ND) options based on lengths provided within the options themselves without sufficient validation. A malformed option with an invalid length can cause the parser to read beyond the allocated buffer or attempt to process a source Link-Layer Address (LLADDR) that is too short for an Ethernet address. This is a classic bounds-checking error that can result in a kernel panic (Denial of Service). The fix involves validating option lengths against the remaining option area and ensuring the LLADDR option is large enough for an Ethernet address before processing.

Affected products

  • Linux Linux Kernel Fixed in 259466f, 82a42ec, 837392a, 8508379, c49b925, e0bfd6d, e71303a, ee02d89
  • 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

  • 2026-03-26: disclosed: Initial patch authored
  • 2026-05-01: advisory: CVE published
  • 2026-07-14: other: Siemens advisory added to record

References

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