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

Source: https://junglewise.ai/threats/cve-2026-43025-linux-kernel-netfilter-out-of-bounds-read-in-ctnetlink  
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-2026-43025 · 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](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-2026-43025 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

- [https://git.kernel.org/stable/c/0f6c33697ccfac6499d0b7a4dbdec5d3a3a566cd](https://git.kernel.org/stable/c/0f6c33697ccfac6499d0b7a4dbdec5d3a3a566cd)
- [https://git.kernel.org/stable/c/187b6ec5229ea93cb04c4f6d3b52efc80f513d0d](https://git.kernel.org/stable/c/187b6ec5229ea93cb04c4f6d3b52efc80f513d0d)
- [https://git.kernel.org/stable/c/21a04c31db4057deec85fcd6cc63d720b38819c3](https://git.kernel.org/stable/c/21a04c31db4057deec85fcd6cc63d720b38819c3)
- [https://git.kernel.org/stable/c/2ea0f35f235f70c133ad61fe05ba013753b978c6](https://git.kernel.org/stable/c/2ea0f35f235f70c133ad61fe05ba013753b978c6)
- [https://git.kernel.org/stable/c/917b61fa2042f11e2af4c428e43f08199586633a](https://git.kernel.org/stable/c/917b61fa2042f11e2af4c428e43f08199586633a)
- [https://git.kernel.org/stable/c/e135f8e8212cbed12a03ab8dec77fa1247139897](https://git.kernel.org/stable/c/e135f8e8212cbed12a03ab8dec77fa1247139897)
- [https://cert-portal.siemens.com/productcert/html/ssa-019113.html](https://cert-portal.siemens.com/productcert/html/ssa-019113.html)

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