CVE-2026-43025: Linux Kernel Netfilter out-of-bounds read in ctnetlink

CVE-2026-43025 · Severity: high · CVSS 7.3 · Published 2026-05-01

A vulnerability in the Linux kernel's networking subsystem could allow a local attacker to read sensitive information from the system's memory. The issue exists in the Netfilter component, which manages network traffic filtering and connection tracking. An exploit could lead to a system crash or the exposure of internal kernel data, potentially compromising the security of the entire operating system.

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-2026-43025 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-43025 being exploited in the wild.
How severe is CVE-2026-43025?
High severity, with a CVSS score of 7.3, published 1 May 2026.
Which products and versions are affected?
Linux Kernel All versions prior to fixed stable releases (e.g., 6.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-2026-43025?
A patch was published on 2026-04-11: Fix committed to Linux stable tree Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-43025 attacked?
It is attacked with local access, in an operating system.
Am I affected by CVE-2026-43025?
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's netfilter/ctnetlink component due to improper validation of user-supplied helper names in connection tracking expectations. When a userspace process provides a different helper than the existing master conntrack helper via CTA_EXPECT_CLASS, the kernel fails to properly bound the request, leading to a slab-out-of-bounds read in nf_ct_expect_related_report. A local attacker with low privileges can exploit this to read bytes of kernel memory beyond the expectation boundary or cause a kernel panic (DoS). The fix involves ignoring explicit helper suggestions from userspace and strictly using the existing master conntrack helper.

Affected products

  • Linux Linux Kernel All versions prior to fixed stable releases (e.g., 6.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

  • 2026-05-01: advisory: Initial CVE publication
  • 2026-04-11: patched: Fix committed to Linux stable tree

References

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