Siemens SIMATIC S7-1500 TM MFP Improper Input Validation (CVE-2026-31685)

critical Tenable OT Security Plugin ID 506385

Synopsis

The remote OT asset is affected by a vulnerability.

Description

In the Linux kernel, the following vulnerability has been resolved:

netfilter: ip6t_eui64: reject invalid MAC header for all packets

`eui64_mt6()` derives a modified EUI-64 from the Ethernet source address and compares it with the low 64 bits of the IPv6 source address.

The existing guard only rejects an invalid MAC header when `par->fragoff != 0`. For packets with `par->fragoff == 0`, `eui64_mt6()` can still reach `eth_hdr(skb)` even when the MAC header is not valid.

Fix this by removing the `par->fragoff != 0` condition so that packets with an invalid MAC header are rejected before accessing `eth_hdr(skb)`.

This plugin only works with Tenable.ot.
Please visit https://www.tenable.com/products/tenable-ot for more information.

Solution

Refer to the vendor advisory.

Plugin Details

Severity: Critical

ID: 506385

File Name: tenable_ot_siemens_CVE-2026-31685.nasl

Version: 1.2

Type: Remote

Family: Tenable.ot

Published: 10/20/2026

Updated: 10/21/2026

Supported Sensors: Tenable OT Security

Risk Information

VPR

Risk Factor: Medium

Score: 4.5

Percentile: 57.48

CVSS v2

Risk Factor: High

Base Score: 9.7

Temporal Score: 7.2

Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:P/A:C

CVSS Score Source: CVE-2026-31685

CVSS v3

Risk Factor: Critical

Base Score: 9.4

Temporal Score: 8.2

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/o:siemens:simatic_s7-1500_tm_mfp

Required KB Items: Tenable.ot/Siemens

Exploit Ease: No known exploits are available

Patch Publication Date: 10/13/2026

Vulnerability Publication Date: 10/13/2026

Reference Information

CVE: CVE-2026-31685

CWE: 20

Detections

Analytics