CVE-2025-41719 is a vulnerability identified in Sauter's modulo 6 devices, specifically the modu680-AS model. The root cause is improper validation of syntactic correctness of input (CWE-1286), which allows a remote attacker with low privileges to send a crafted sequence of unsupported characters to the device's webserver interface. This input manipulation corrupts the user storage on the device, resulting in the deletion of all previously configured user accounts. Subsequently, the device reverts to a default Administrator account with a known default password, effectively granting the attacker full administrative access. The vulnerability is remotely exploitable over the network (AV:N), requires low attack complexity (AC:L), and only low privileges (PR:L), with no user interaction needed (UI:N). The scope is unchanged (S:U), but the impact on confidentiality, integrity, and availability is high (C:H/I:H/A:H), as the attacker gains control over the device and can manipulate or disrupt its functions. The device is typically used in building automation and industrial control environments, where unauthorized access could lead to operational disruptions or safety risks. No patches are currently available, and no exploits have been observed in the wild, but the severity and ease of exploitation make this a critical issue to address promptly.

For European organizations, particularly those relying on Sauter modulo 6 devices for building automation, HVAC control, or industrial processes, this vulnerability poses a significant risk. Exploitation can lead to unauthorized administrative access, allowing attackers to manipulate device configurations, disrupt operations, or pivot to other network segments. The deletion of all user accounts and fallback to a default password undermines all existing access controls, increasing the likelihood of persistent compromise. Critical infrastructure facilities, commercial buildings, and manufacturing plants using these devices could experience operational downtime, safety hazards, or data breaches. Given the high CVSS score (8.8) and the potential for complete device takeover, the impact on confidentiality, integrity, and availability is severe. Additionally, the lack of patches increases exposure time, making proactive mitigation essential.

1. Immediately segment and isolate Sauter modulo 6 devices from general enterprise networks to limit exposure to potential attackers. 2. Implement strict network access controls and firewall rules to restrict management interface access to trusted administrators only. 3. Monitor network traffic for unusual sequences or unsupported characters targeting the device's webserver interface, enabling early detection of exploitation attempts. 4. Enforce multi-factor authentication and strong password policies on all management interfaces where possible, even if the device reverts to default credentials. 5. Maintain an inventory of all affected devices and prioritize their monitoring and protection. 6. Engage with Sauter or authorized vendors to obtain patches or firmware updates as soon as they become available. 7. Consider deploying intrusion detection/prevention systems (IDS/IPS) with signatures tailored to detect exploitation attempts of this vulnerability. 8. Conduct regular security audits and penetration tests focusing on building automation and industrial control systems to identify and remediate similar weaknesses.