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

Source: https://junglewise.ai/threats/cve-2026-31752-linux-kernel-out-of-bounds-read-in-bridge-nd-option-parsing  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-01. Updated: 2026-07-14  
License: CC BY 4.0 with a link back

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](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-2026-31752 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

- [https://git.kernel.org/stable/c/259466f76f5a2148aff11134e68f4b4c6d52725b](https://git.kernel.org/stable/c/259466f76f5a2148aff11134e68f4b4c6d52725b)
- [https://git.kernel.org/stable/c/82a42eceec7c6bdb0e0da94c0542a173b7ea57f2](https://git.kernel.org/stable/c/82a42eceec7c6bdb0e0da94c0542a173b7ea57f2)
- [https://git.kernel.org/stable/c/837392a38445729c22e03d3abcf33f07763efd85](https://git.kernel.org/stable/c/837392a38445729c22e03d3abcf33f07763efd85)
- [https://git.kernel.org/stable/c/850837965af15707fd3142c1cf3c5bfaf022299b](https://git.kernel.org/stable/c/850837965af15707fd3142c1cf3c5bfaf022299b)
- [https://git.kernel.org/stable/c/c49b9256bbacb6a135654aebd12e4c0e87166b7c](https://git.kernel.org/stable/c/c49b9256bbacb6a135654aebd12e4c0e87166b7c)
- [https://git.kernel.org/stable/c/e0bfd6d4dc77ab345b6c65eef0cfe9b2f69085aa](https://git.kernel.org/stable/c/e0bfd6d4dc77ab345b6c65eef0cfe9b2f69085aa)
- [https://git.kernel.org/stable/c/e71303a9190496136e240c4f2872b7b0b16027a7](https://git.kernel.org/stable/c/e71303a9190496136e240c4f2872b7b0b16027a7)

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