CVE-2022-39158 is a vulnerability identified in Siemens RUGGEDCOM i800 devices, specifically affecting all versions prior to V4.3.8. The vulnerability arises from improper handling of partial HTTP requests, which allows an attacker to exploit the device using a slowloris attack. Slowloris is a type of denial-of-service (DoS) attack that works by opening multiple HTTP connections to the target device and sending partial requests very slowly, thereby exhausting the device's resources such as connection slots and memory buffers. Because the device does not properly manage these incomplete requests, it remains tied up until the attack stops, effectively denying legitimate users access to the device or its services. This vulnerability falls under CWE-400, which pertains to uncontrolled resource consumption, indicating that the device lacks adequate controls to limit resource usage under attack conditions. The attack can be launched remotely without authentication or user interaction, making it accessible to any attacker with network access to the device. Although no known exploits have been reported in the wild, the vulnerability poses a persistent DoS risk until mitigated. Siemens has released version 4.3.8 as a fixed version, but no direct patch links are provided in the information. The RUGGEDCOM i800 is typically used in industrial and critical infrastructure environments, including utilities and transportation sectors, where network reliability and uptime are crucial.

For European organizations, especially those operating in critical infrastructure sectors such as energy, transportation, and industrial automation, this vulnerability could lead to significant operational disruptions. The RUGGEDCOM i800 devices are often deployed in harsh or remote environments to provide ruggedized networking capabilities. A successful slowloris attack could cause prolonged denial of service, potentially interrupting communication between control centers and field devices. This disruption could impact monitoring, control, and safety systems, leading to degraded service quality, delayed responses to operational incidents, and in worst cases, safety hazards. Additionally, the inability to access or manage affected devices during an attack could delay incident response and remediation efforts. While the vulnerability does not directly lead to data breaches or integrity compromises, the availability impact alone can have cascading effects on business continuity and regulatory compliance, especially under the EU's NIS Directive and other critical infrastructure protection frameworks.

Organizations should prioritize upgrading all Siemens RUGGEDCOM i800 devices to firmware version 4.3.8 or later, which addresses this vulnerability. In environments where immediate patching is not feasible, network-level mitigations should be implemented. These include deploying web application firewalls (WAFs) or intrusion prevention systems (IPS) configured to detect and block slowloris-style attacks by limiting the number of simultaneous connections from a single source and enforcing timeouts on incomplete HTTP requests. Network segmentation can reduce exposure by isolating RUGGEDCOM devices from general-purpose networks and restricting access to trusted management hosts only. Monitoring network traffic for abnormal connection patterns indicative of slowloris attacks can enable early detection and response. Additionally, Siemens device configurations should be reviewed to ensure that any available rate limiting or connection management features are enabled and properly tuned. Incident response plans should incorporate procedures for mitigating DoS conditions affecting critical network devices.