CVE-2021-33539 : Exploit Details and Defense Strategies

This article provides detailed information about CVE-2021-33539, a vulnerability in Weidmueller Industrial WLAN devices that allows an attacker to bypass authentication. The article covers the impact, technical details, and mitigation strategies associated with this CVE.

Understanding CVE-2021-33539

In Weidmueller Industrial WLAN devices in multiple versions, an exploitable authentication bypass vulnerability exists due to hostname processing. This vulnerability can allow an attacker to bypass web authentication by sending authenticated SNMP requests.

What is CVE-2021-33539?

A specially configured device hostname can cause the device to interpret selected remote traffic as local traffic, resulting in an authentication bypass.

The Impact of CVE-2021-33539

The CVSS v3.1 base score for CVE-2021-33539 is 7.2, indicating a high severity issue with impacts on confidentiality, integrity, and availability. The attack complexity is low, and privileges required are high.

Technical Details of CVE-2021-33539

Vulnerability Description

The vulnerability allows an attacker to send authenticated SNMP requests to trick the device into interpreting remote traffic as local, bypassing web authentication.

Affected Systems and Versions

Weidmueller Industrial WLAN devices versions IE-WL-BL-AP-CL-EU, IE-WLT-BL-AP-CL-EU, IE-WL-BL-AP-CL-US, IE-WLT-BL-AP-CL-US, IE-WL-VL-AP-BR-CL-EU, IE-WLT-VL-AP-BR-CL-EU, IE-WL-VL-AP-BR-CL-US, and IE-WLT-VL-AP-BR-CL-US are affected by this vulnerability.

Exploitation Mechanism

Attackers can exploit this vulnerability by sending specially crafted SNMP requests to the affected devices, allowing them to bypass authentication mechanisms.

Mitigation and Prevention

Immediate Steps to Take

Users are advised to apply the provided patches for affected versions:

For IE-WL(T)-BL-AP-CL-XX: Versions V1.16.21 (Build 21010513) and greater are fixed.
For IE-WL(T)-VL-AP-CL-XX: Versions V1.11.13 (Build 21010513) and greater are fixed.

Long-Term Security Practices

It is crucial to regularly update the firmware of Weidmueller Industrial WLAN devices and follow best security practices to prevent future vulnerabilities.

Patching and Updates

Users should regularly check for security updates and apply patches provided by Weidmueller to ensure the security of their Industrial WLAN devices.