Siemens SIMATIC S7-1500 Cross-site Scripting (CVE-2026-25786)

critical Tenable OT Security Plugin ID 505539

Synopsis

The remote OT asset is affected by a vulnerability.

Description

Affected devices do not properly validate and sanitize PLC/station name rendered on the 'communication' parameters page of the web interface. This could allow an authenticated attacker who is authorized to download a TIA project into the product, to inject malicious scripts into the page. If a benign user with appropriate rights accesses the 'communication' parameters page, the malicious code would be executed in the scope of their web session.

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

Solution

Update to V2.9.9 or later version. For CPU 1516T/TF, 1517, and 1518 series, update to V3.1.6 or later. As a workaround, restrict TIA project downloads to trusted personnel only. See the vendor advisory for product-specific version requirements.

Plugin Details

Severity: Critical

ID: 505539

File Name: tenable_ot_siemens_CVE-2026-25786.nasl

Version: 1.1

Type: Remote

Family: Tenable.ot

Published: 7/6/2026

Updated: 7/6/2026

Supported Sensors: Tenable OT Security

Risk Information

VPR

Risk Factor: Medium

Score: 5

Percentile: 94.27

CVSS v3

Risk Factor: Critical

Base Score: 9.1

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

Vulnerability Information

CPE: cpe:/o:siemens:simatic_et200pro_firmware, cpe:/o:siemens:simatic_s7-1500_cpu_firmware, cpe:/o:siemens:simatic_et200sp_firmware, cpe:/o:siemens:siplus_s7-1500_cpu_firmware

Required KB Items: Tenable.ot/Siemens

Patch Publication Date: 5/12/2026

Vulnerability Publication Date: 5/12/2026

Reference Information

CVE: CVE-2026-25786

CWE: 79

ICSA: 26-134-15

Detections

Analytics