Siemens SIMATIC S7-1500 Improper Authentication (CVE-2023-27535)

medium Tenable OT Security Plugin ID 504300

Synopsis

The remote OT asset is affected by a vulnerability.

Description

An authentication bypass vulnerability exists in libcurl <8.0.0 in the FTP connection reuse feature that can result in wrong credentials being used during subsequent transfers. Previously created connections are kept in a connection pool for reuse if they match the current setup. However, certain FTP settings such as CURLOPT_FTP_ACCOUNT, CURLOPT_FTP_ALTERNATIVE_TO_USER, CURLOPT_FTP_SSL_CCC, and CURLOPT_USE_SSL were not included in the configuration match checks, causing them to match too easily. This could lead to libcurl using the wrong credentials when performing a transfer, potentially allowing unauthorized access to sensitive information.

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: Medium

ID: 504300

Version: 1.1

Type: remote

Family: Tenable.ot

Published: 11/13/2025

Updated: 11/13/2025

Supported Sensors: Tenable OT Security

Risk Information

VPR

Risk Factor: Medium

Score: 4.4

CVSS v3

Risk Factor: Medium

Base Score: 5.9

Temporal Score: 5.3

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

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

Vulnerability Information

CPE: cpe:/o:siemens:scalance_xcm332_firmware:2.4, cpe:/o:siemens:scalance_xrh334_%2824_v_dc%2c_8xfo%2c_cc%29_firmware:2.4, cpe:/o:siemens:scalance_xrm334_%28230_v_ac%2c_8xfo%29_firmware:2.4, cpe:/o:siemens:scalance_xch328_firmware:2.4, cpe:/o:siemens:scalance_xrm334_%2824_v_dc%2c_12xfo%29_firmware:2.4, cpe:/o:siemens:scalance_xrm334_%2824_v_dc%2c_8xfo%29_firmware:2.4, cpe:/o:siemens:scalance_xrm334_%282x230_v_ac%2c_12xfo%29_firmware:2.4, cpe:/o:siemens:scalance_xrm334_%28230_v_ac%2c_12xfo%29_firmware:2.4, cpe:/o:siemens:siplus_s7-1500_cpu_firmware:3.1.5, cpe:/o:siemens:scalance_xrm334_%282x230_v_ac%2c_8xfo%29_firmware:2.4, cpe:/o:siemens:scalance_xcm328_firmware:2.4, cpe:/o:siemens:scalance_xcm324_firmware:2.4, cpe:/o:siemens:simatic_s7-1500_cpu_firmware:3.1.5

Required KB Items: Tenable.ot/Siemens

Exploit Ease: No known exploits are available

Patch Publication Date: 12/12/2023

Vulnerability Publication Date: 12/12/2023

Reference Information

CVE: CVE-2023-27535

CWE: 287

Detections

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