Siemens SIMATIC S7-1500 Cross-site Scripting (CVE-2026-25789)

high Tenable OT Security Plugin ID 505540

Synopsis

The remote OT asset is affected by a vulnerability.

Description

Affected devices do not properly validate and sanitize filenames on the Firmware Update page. This could allow a remote attacker to social engineer the user into selecting a modified firmware file.
This would result in malicious JavaScript execution in the context of the authenticated user's session without requiring the file to be uploaded, potentially leading to session hijacking.

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: High

ID: 505540

File Name: tenable_ot_siemens_CVE-2026-25789.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: 4.9

Percentile: 57.88

CVSS v3

Risk Factor: High

Base Score: 7.1

Vector: CVSS:3.0/AV:N/AC:H/PR:L/UI:R/S:U/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-2026-25789

CWE: 79

ICSA: 26-134-15

Detections

Analytics