CVE-2025-3092 is a vulnerability identified in the Helmholz myREX24 device, which allows an unauthenticated remote attacker to enumerate valid usernames via an unprotected endpoint. This vulnerability is classified under CWE-204: Observable Response Discrepancy, meaning the system's responses differ in a way that reveals information about the validity of usernames. Specifically, the attacker can send requests to the device and observe differences in responses or timing that confirm whether a username exists in the system without needing any authentication or user interaction. The affected product, myREX24, is a device produced by Helmholz, likely used in building automation or similar industrial control environments. The CVSS v3.1 base score is 7.5, indicating a high severity level. The vector string (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N) reveals that the attack can be performed remotely over the network (AV:N), requires low attack complexity (AC:L), no privileges (PR:N), no user interaction (UI:N), and affects confidentiality (C:H) but not integrity or availability. No patches or known exploits in the wild have been reported as of the publication date (June 24, 2025). The vulnerability allows attackers to gather valid usernames, which can be leveraged in subsequent targeted attacks such as brute force password attempts, credential stuffing, or social engineering, potentially compromising sensitive systems or data.

For European organizations using Helmholz myREX24 devices, this vulnerability poses a significant risk to confidentiality. The ability to enumerate valid usernames remotely and without authentication exposes these organizations to increased risk of credential-based attacks. Since the vulnerability does not affect integrity or availability directly, the immediate operational impact may be limited; however, the exposure of valid usernames can facilitate further exploitation, including unauthorized access if weak or reused passwords are present. This is particularly concerning for critical infrastructure, industrial control systems, or building automation systems where myREX24 devices are deployed, as unauthorized access could lead to espionage, data leakage, or indirect disruption of services. European organizations in sectors such as manufacturing, energy, and facility management that rely on Helmholz products should be aware of this risk. Additionally, the lack of authentication requirement and low attack complexity means attackers can easily automate username enumeration at scale, increasing the threat surface.

1. Network Segmentation: Isolate myREX24 devices from public or less trusted networks to limit exposure of the vulnerable endpoint. 2. Access Controls: Implement strict firewall rules to restrict access to the device management interfaces only to authorized IP addresses or VPNs. 3. Monitoring and Logging: Enable detailed logging on the devices and network perimeter to detect unusual enumeration attempts or repeated access patterns indicative of reconnaissance. 4. Credential Policies: Enforce strong, unique passwords and consider multi-factor authentication if supported by the device to reduce risk from credential stuffing or brute force attacks. 5. Vendor Engagement: Engage with Helmholz to obtain information on patches or firmware updates addressing this vulnerability and apply them promptly once available. 6. Application Layer Gateway: Deploy reverse proxies or API gateways that can normalize responses and prevent observable discrepancies that enable username enumeration. 7. Incident Response Preparation: Prepare playbooks for responding to detected enumeration or brute force attempts, including account lockout policies and alerting mechanisms. These measures go beyond generic advice by focusing on network-level protections, proactive monitoring, and compensating controls until a patch is available.