Siemens SIMATIC S7-1500 TM MFP Use of Incorrect Operator (CVE-2026-43114)

critical Tenable OT Security Plugin ID 506390

Synopsis

The remote OT asset is affected by a vulnerability.

Description

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

netfilter: nft_set_pipapo_avx2: don't return non-matching entry on expiry

New test case fails unexpectedly when avx2 matching functions are used.

The test first loads a ranomly generated pipapo set with 'ipv4 . port' key, i.e. nft -f foo.

This works. Then, it reloads the set after a flush:
(echo flush set t s; cat foo) | nft -f -

This is expected to work, because its the same set after all and it was already loaded once.

But with avx2, this fails: nft reports a clashing element.

The reported clash is of following form:

We successfully re-inserted a . b c . d

Then we try to insert a . d

avx2 finds the already existing a . d, which (due to 'flush set') is marked as invalid in the new generation. It skips the element and moves to next.

Due to incorrect masking, the skip-step finds the next matching element *only considering the first field*,

i.e. we return the already reinserted 'a . b', even though the last field is different and the entry should not have been matched.

No such error is reported for the generic c implementation (no avx2) or when the last field has to use the 'nft_pipapo_avx2_lookup_slow' fallback.

Bisection points to 7711f4bb4b36 ('netfilter: nft_set_pipapo: fix range overlap detection') but that fix merely uncovers this bug.

Before this commit, the wrong element is returned, but erronously reported as a full, identical duplicate.

The root-cause is too early return in the avx2 match functions.
When we process the last field, we should continue to process data until the entire input size has been consumed to make sure no stale bits remain in the map.

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: 506390

File Name: tenable_ot_siemens_CVE-2026-43114.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: Medium

Score: 4.3

Percentile: 53.49

CVSS v3

Risk Factor: Critical

Base Score: 9.4

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

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-2026-43114

CWE: 480

Detections

Analytics