Siemens SIMATIC S7-1500 TM MFP Improper Input Validation (CVE-2026-45843)

high Tenable OT Security Plugin ID 506313

Synopsis

The remote OT asset is affected by a vulnerability.

Description

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

slip: bound decode() reads against the compressed packet length

slhc_uncompress() parses a VJ-compressed TCP header by advancing a pointer through the packet via decode() and pull16(). Neither helper bounds-checks against isize, and decode() masks its return with & 0xffff so it can never return the -1 that callers test for -- those error paths are dead code.

A short compressed frame whose change byte requests optional fields lets decode() read past the end of the packet. The over-read bytes are folded into the cached cstate and reflected into subsequent reconstructed packets.

Make decode() and pull16() take the packet end pointer and return -1 when exhausted. Add a bounds check before the TCP-checksum read.
The existing == -1 tests now do what they were always meant to.

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: High

ID: 506313

File Name: tenable_ot_siemens_CVE-2026-45843.nasl

Version: 1.1

Type: Remote

Family: Tenable.ot

Published: 10/20/2026

Updated: 10/20/2026

Supported Sensors: Tenable OT Security

Risk Information

VPR

Risk Factor: Low

Score: 3.5

Percentile: 51.96

CVSS v3

Risk Factor: High

Base Score: 8.2

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

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-2026-45843

CWE: 20

Detections

Analytics