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

Source: https://junglewise.ai/threats/cve-2026-31674-linux-kernel-out-of-bounds-access-in-netfilter-ip6t-rt  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-25. Updated: 2026-07-14  
License: CC BY 4.0 with a link back

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](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-2026-31674 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

- [https://git.kernel.org/stable/c/13e3e30ed3b5b67cc1db2bd58a5d09b0f07debfa](https://git.kernel.org/stable/c/13e3e30ed3b5b67cc1db2bd58a5d09b0f07debfa)
- [https://git.kernel.org/stable/c/29ea965a1353bc8303877422f79c8211e9ba9c55](https://git.kernel.org/stable/c/29ea965a1353bc8303877422f79c8211e9ba9c55)
- [https://git.kernel.org/stable/c/9d3f027327c2fa265f7f85ead41294792c3296ed](https://git.kernel.org/stable/c/9d3f027327c2fa265f7f85ead41294792c3296ed)
- [https://git.kernel.org/stable/c/a28ebf6f99de270d6338ccdc3b49f3e818f99b7b](https://git.kernel.org/stable/c/a28ebf6f99de270d6338ccdc3b49f3e818f99b7b)
- [https://git.kernel.org/stable/c/af9b7e2b765966457f4ec23be5bd34a141f89574](https://git.kernel.org/stable/c/af9b7e2b765966457f4ec23be5bd34a141f89574)
- [https://git.kernel.org/stable/c/c6a503a9f4debc654e3a6a7ca1f7fce6a9953c59](https://git.kernel.org/stable/c/c6a503a9f4debc654e3a6a7ca1f7fce6a9953c59)
- [https://git.kernel.org/stable/c/d8795fde1f78669a87c87ac29fceab2f104daa8c](https://git.kernel.org/stable/c/d8795fde1f78669a87c87ac29fceab2f104daa8c)

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