WAGO: Web-Based Management Denial of Service

Web-Based Management (wbm) of WAGO PLCs is prone to a denial of service attack.

VDE-2020-007 (2020-03-09 10:10 UTC+0100)

CVE Identifier

CVE-2019-5149

Severity

5.3 (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L)

Affected Vendors

WAGO

Affected Products

Article Name	Article Number	Version
Series PFC100	750-81xx/xxx-xxx	All FW versions => 5 are affected
Series PFC200	750-82xx/xxx-xxx
Touch Panel 600 Standard Line	762-4xxx
Touch Panel 600 Advanced Line	762-5xxx
Touch Panel 600 Marine Line	762-6xxx

Vulnerability Type

Insufficient Resource Pool (CWE-410)

Summary

The Web-Based Management (WBM) of WAGOs programmable logic controller (PLC) is typically used for commissioning and update. The controller is an embedded device which has limited resources. The vulnerability described here takes advantage of this fact.
With special crafted requests it is possible to have a denial of service of the WBM.

Impact

The default configuration of the web server limits the number of concurrent processes, which can be abused to cause a DoS of the WBM.
This vulnerability allows an attacker, who has access to the device, to cause a denial of service of the WBM, by sending special crafted requests.

Solution

Due to the limited resources on the embedded device, it is necessary to protect it from unauthorized access such as denial of service attacks.

Mitigation

Follow the instructions in WAGOs handbook Cyber Security for Controller
Restrict network access to the device.
Do not directly connect the device to the internet

Reported by

This vulnerability was reported by Daniel Patrick DeSantis, Cisco Talos to WAGO. Coordination done by CERT@VDE.