CVE-2026-31674: Linux Kernel out-of-bounds access in netfilter ip6t_rt

CVE-2026-31674 · Severity: high · CVSS 7.1 · Published 2026-04-25

A vulnerability exists in the Linux kernel's networking subsystem that could allow a local user to crash the system or potentially access sensitive information. The issue occurs when the system processes specifically malformed IPv6 routing rules. This affects various Linux-based systems, including certain Siemens industrial controllers, potentially impacting operational availability.

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-2026-31674 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-31674 being exploited in the wild.
How severe is CVE-2026-31674?
High severity, with a CVSS score of 7.1, published 25 April 2026.
Which products and versions are affected?
Linux Kernel 2.6.12-rc2 to 6.13.x; 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-2026-31674?
A patch was published on 2026-03-26: Initial patch committed to Linux kernel tree Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-31674 attacked?
It is attacked with local access, in an operating system.
Am I affected by CVE-2026-31674?
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

An out-of-bounds read vulnerability exists in the Linux kernel netfilter module (ip6t_rt). The function rt_mt6_check() fails to validate that the 'addrnr' field in the 'rtinfo' structure stays within the bounds of the 'addrs[]' array (defined by IP6T_RT_HOPS). A local attacker with permissions to modify netfilter rules can provide a malformed rule with an oversized addrnr. When the match logic in rt_mt6() subsequently processes this rule, it may perform an out-of-bounds access, leading to a kernel crash (DoS) or information disclosure. The fix involves adding a bounds check during rule installation to reject malformed rules.

Affected products

  • Linux Linux Kernel 2.6.12-rc2 to 6.13.x
  • 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

  • 2026-03-25: disclosed: Vulnerability reported by researchers
  • 2026-03-26: patched: Initial patch committed to Linux kernel tree
  • 2026-04-25: advisory: CVE published

References

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