CVE-2026-31682: Linux Kernel out-of-bounds read in bridge br_nd_send

CVE-2026-31682 · Severity: critical · CVSS 9.1 · Published 2026-04-25

A vulnerability exists in the Linux kernel's network bridging component, which is used to connect different network segments. An attacker could exploit this flaw by sending specially crafted network discovery packets, potentially leading to a system crash or unauthorized access to sensitive information in memory. This affects various Linux-based systems and industrial controllers from Siemens that utilize the impacted kernel versions.

Technologies: 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: Siemens.

Quick answers

Is CVE-2026-31682 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-31682 being exploited in the wild.
How severe is CVE-2026-31682?
Critical severity, with a CVSS score of 9.1, published 25 April 2026.
Which products and versions are affected?
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-2026-31682?
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-2026-31682 attacked?
It is attacked over the network, in an operating system.
Am I affected by CVE-2026-31682?
Check whether you run Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP, Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP or Siemens SIPLUS S7-1500 CPU 1518-4 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

A vulnerability in the br_nd_send() function of the Linux kernel's bridge module arises because the function assumes Neighbor Discovery (ND) options are located in the linear portion of a socket buffer (skb). While callers guarantee the availability of the ICMPv6 header and target address, the option area may remain non-linear. An attacker can trigger an out-of-bounds read by providing a non-linear skb, which could lead to a kernel panic (DoS) or information disclosure. The fix involves linearizing the skb before parsing ND options and deriving the message structure from the linear network header. This issue is tracked as CVE-2026-31682 and has been patched in multiple stable kernel branches.

Affected products

  • Linux Linux Kernel Fixed in various stable branches including 2ba4caba423ed94d63006eb1d2227b0332ab7fcd and others
  • 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: other: Initial patch authored
  • 2026-04-25: disclosed: Vulnerability published

References

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