CVE-2023-35120 in M-Bus SoftwarePack 900S
Summary
by MITRE • 07/07/2023
PiiGAB M-Bus is vulnerable to cross-site request forgery. An attacker who wants to execute a certain command could send a phishing mail to the owner of the device and hope that the owner clicks on the link. If the owner of the device has a cookie stored that allows the owner to be logged in, then the device could execute the GET or POST link request.
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Analysis
by VulDB Data Team • 07/25/2023
The PiiGAB M-Bus device presents a critical cross-site request forgery vulnerability that exploits the fundamental weakness in web application security models. This vulnerability resides in the authentication and session management mechanisms of the device's web interface, where persistent cookies are used to maintain user sessions without proper CSRF protection measures. The vulnerability allows attackers to execute unauthorized commands on behalf of authenticated users simply by luring them into clicking malicious links embedded in phishing emails or web pages. The device's web interface fails to implement proper anti-CSRF tokens or referer validation checks, creating an exploitable condition where session cookies are automatically transmitted with every request regardless of the origin. This flaw directly violates the principle of least privilege and demonstrates inadequate security design in the device's web services architecture.
The technical exploitation of this vulnerability follows a well-established pattern that aligns with CWE-352, which specifically addresses cross-site request forgery weaknesses in web applications. Attackers can craft malicious web pages or email attachments containing embedded links that, when clicked by an authenticated user, automatically submit requests to the M-Bus device's web interface. The device processes these requests with the user's existing session cookies, effectively executing commands as if the user had initiated them directly. The vulnerability is particularly dangerous because it requires minimal user interaction beyond clicking a link, making it highly effective for social engineering campaigns. The device's lack of request origin verification and absence of CSRF tokens creates a persistent threat vector that remains active as long as the user maintains an active session.
The operational impact of this vulnerability extends beyond simple unauthorized command execution to encompass potential system compromise and data manipulation. An attacker could leverage this vulnerability to modify device configurations, access sensitive data, or even execute arbitrary code depending on the device's capabilities. The attack surface is particularly concerning for industrial control systems and smart metering applications where M-Bus devices are commonly deployed. The vulnerability creates a persistent backdoor that remains active until the user's session expires or the device is manually rebooted. This makes it especially dangerous in environments where physical access is limited and remote management is required, as the attacker could maintain persistent access without detection. The vulnerability also affects the device's integrity and availability, potentially leading to denial of service or unauthorized data collection.
Mitigation strategies for this vulnerability should focus on implementing proper CSRF protection mechanisms as recommended by the OWASP Top Ten and NIST cybersecurity frameworks. The device must implement anti-CSRF tokens that are generated per session and validated for each request, ensuring that requests originate from legitimate sources within the same session context. Additionally, the device should implement proper referer header validation and implement SameSite cookie attributes to prevent automatic cookie transmission across different origins. Network segmentation and access control measures should be deployed to limit exposure of the device's web interface to trusted networks only. Regular security updates and patch management procedures should be established to address such vulnerabilities promptly. The device manufacturer should also implement comprehensive logging and monitoring capabilities to detect suspicious activities and unauthorized access attempts. Implementation of these controls aligns with the ATT&CK framework's defense in depth principles and helps establish a more robust security posture against similar vulnerabilities in industrial IoT environments.