This vulnerability was reported by Daniel Patrick DeSantis, Cisco Talos to WAGO. Coordination done by CERT@VDE.
| Article No° | Product Name | Affected Version(s) |
|---|---|---|
| 750-81xx/xxx-xxx (PFC100) | >= FW05 | |
| 750-82xx/xxx-xxx (PFC200) | >= FW05 | |
| 762-4xxx | >= FW05 | |
| 762-5xxx | >= FW05 | |
| 762-6xxx | >= FW05 |
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.
The WBM web application on firmwares prior to 03.02.02 and 03.01.07 on the WAGO PFC100 and PFC2000, respectively, runs on a lighttpd web server and makes use of the FastCGI module, which is intended to provide high performance for all Internet applications without the penalties of Web server APIs. However, the default configuration of this module appears to limit the number of concurrent php-cgi processes to two, which can be abused to cause a denial of service of the entire web server. This affects WAGO PFC200 Firmware version 03.00.39(12) and version 03.01.07(13), and WAGO PFC100 Firmware version 03.00.39(12) and version 03.02.02(14).
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.
Mitigation
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.
This vulnerability was reported by Daniel Patrick DeSantis, Cisco Talos to WAGO. Coordination done by CERT@VDE.