CVE-2025-9494 is a high-severity OS command injection vulnerability affecting the Viessmann Vitogate 300 device, specifically version 1. The vulnerability exists in the `/cgi-bin/vitogate.cgi` endpoint when the `form` JSON parameter is set to `form-0-2`. The root cause is improper input sanitization in a function located at offset 0x21c24, which interpolates user-supplied input into a format string passed to the `popen()` system call. Because `popen()` executes shell commands, this flaw allows an authenticated attacker to inject arbitrary OS commands, leading to remote code execution on the affected device. The vulnerability requires authentication but no user interaction, and the attacker can fully compromise confidentiality, integrity, and availability of the device. The CVSS v4.0 score is 8.5 (high), reflecting the ease of exploitation given low attack complexity and the severe impact on the device. No public exploits are known in the wild yet, and no patches have been published at the time of disclosure. The Vitogate 300 is typically used as a gateway device in heating and building management systems, making it a critical component in industrial and building automation environments. Exploitation could allow attackers to disrupt heating controls, exfiltrate sensitive operational data, or pivot into broader enterprise or industrial networks.

For European organizations, the impact of this vulnerability is significant due to the widespread use of Viessmann heating and building management solutions across residential, commercial, and industrial sectors. Successful exploitation could lead to unauthorized control over heating systems, causing operational disruptions, safety hazards, and potential physical damage in critical infrastructure such as hospitals, data centers, and manufacturing plants. Confidential data related to building management and occupancy could be exposed, violating privacy regulations such as GDPR. Furthermore, compromised Vitogate 300 devices could serve as footholds for lateral movement within enterprise networks, increasing the risk of broader cyberattacks. The high integrity and availability impact could also affect energy efficiency and compliance with environmental standards. Given the authentication requirement, insider threats or compromised credentials pose a particular risk. The lack of patches increases exposure until mitigations are applied.

1. Immediately restrict access to the `/cgi-bin/vitogate.cgi` endpoint to trusted administrators only, ideally via network segmentation and firewall rules limiting access to management interfaces. 2. Enforce strong authentication mechanisms and rotate credentials regularly to reduce the risk of credential compromise. 3. Monitor logs for unusual activity related to the `form-0-2` parameter or unexpected command execution attempts. 4. If possible, disable or restrict the vulnerable CGI endpoint until a vendor patch is available. 5. Employ network intrusion detection systems (NIDS) with signatures targeting command injection patterns specific to this vulnerability. 6. Engage with Viessmann support to obtain timelines for patches or firmware updates and apply them promptly once available. 7. Conduct internal audits of all Vitogate 300 devices to identify affected versions and isolate or upgrade them. 8. Implement strict change management and incident response plans tailored to building management systems to quickly respond to any exploitation attempts.