CVE-2025-26409 is a medium-severity vulnerability affecting Wattsense Bridge devices, identified as a missing protection mechanism for an alternate hardware interface (CWE-1299). The vulnerability arises because the device’s printed circuit board (PCB) exposes a serial interface that can be accessed physically. Upon connecting to this interface, an attacker can reach the device’s bootloader and a Linux login prompt without requiring authentication. Access to the bootloader allows the attacker to escalate privileges and obtain a root shell on the device, effectively compromising the device’s confidentiality, integrity, and availability. The vulnerability is present in firmware versions prior to BSP 6.4.1, which includes the fix. The attack vector requires physical access to the device’s PCB, meaning remote exploitation is not feasible without prior physical compromise. The CVSS v3.1 score is 6.8, reflecting low attack vector (physical), low attack complexity, no privileges required, no user interaction, and high impact on all three security properties. No known exploits have been reported in the wild as of the publication date. Wattsense Bridge devices are typically used in building automation and energy management systems, making them critical components in smart building infrastructure. The vulnerability could allow attackers to manipulate device operation, extract sensitive information, or disrupt services.

For European organizations, the impact of this vulnerability is significant in environments where Wattsense Bridge devices are deployed for building automation, energy management, or critical infrastructure monitoring. An attacker with physical access could gain root control over the device, potentially leading to unauthorized data access, manipulation of device functions, or disruption of building systems such as HVAC, lighting, or energy metering. This could result in operational downtime, safety risks, and data breaches. Since the vulnerability requires physical access, the risk is elevated in locations with insufficient physical security controls or where devices are installed in publicly accessible or poorly secured areas. The compromise of these devices could also serve as a foothold for lateral movement within organizational networks, increasing the overall risk posture. Given the high confidentiality, integrity, and availability impact, organizations must prioritize remediation to prevent potential sabotage or espionage activities.

To mitigate CVE-2025-26409, European organizations should immediately update all Wattsense Bridge devices to firmware version BSP 6.4.1 or later, which contains the fix for this vulnerability. Physical security controls must be enhanced to restrict unauthorized access to device PCBs, including securing device enclosures, deploying tamper-evident seals, and monitoring access to equipment rooms or installation sites. Organizations should conduct physical audits to identify devices installed in vulnerable locations and relocate or secure them as necessary. Network segmentation should be employed to isolate building automation devices from critical IT infrastructure to limit the impact of any compromise. Additionally, implement logging and monitoring to detect unusual device behavior that could indicate exploitation attempts. Regularly review and update asset inventories to ensure all affected devices are accounted for and patched. Finally, coordinate with Wattsense support for guidance on secure deployment best practices and firmware updates.