CVE-2025-41251 is a high-severity vulnerability affecting multiple versions of VMware NSX, NSX-T, and VMware Cloud Foundation with NSX. The root cause is a weak password recovery mechanism that allows an unauthenticated attacker to enumerate valid usernames remotely. This username enumeration flaw can be leveraged to facilitate brute-force attacks against user credentials, significantly increasing the risk of unauthorized access. The vulnerability is classified under CWE-640, which pertains to weak password recovery mechanisms. Exploitation does not require any prior authentication or user interaction, but the attack complexity is rated as high due to the need for remote access and potentially sophisticated brute-force techniques. The CVSS v3.1 base score is 8.1, indicating a high impact on confidentiality, integrity, and availability. The affected VMware NSX versions include 9.x.x.x, 4.2.x, 4.1.x, and 4.0.x, NSX-T 3.x, and VMware Cloud Foundation versions 5.x and 4.5.x. VMware has released fixed versions such as NSX 9.0.1.0, 4.2.2.2/4.2.3.1, 4.1.2.7, NSX-T 3.2.4.3, and a CCF async patch (KB88287). No workarounds are currently available. The vulnerability was reported by the National Security Agency, underscoring its significance. Although no known exploits are currently in the wild, the potential for credential brute forcing makes this a critical issue for organizations relying on these VMware products for network virtualization and security infrastructure.

For European organizations, this vulnerability poses a significant risk due to the widespread adoption of VMware NSX and related products in enterprise data centers, cloud environments, and critical infrastructure. Successful exploitation could lead to unauthorized access to network virtualization management interfaces, enabling attackers to manipulate network configurations, intercept or redirect traffic, or disrupt services. This compromises confidentiality, integrity, and availability of network resources. Given the remote and unauthenticated attack vector, threat actors could target European enterprises without needing insider access. The username enumeration facilitates targeted brute-force attacks, increasing the likelihood of credential compromise. This is especially concerning for sectors with stringent regulatory requirements such as finance, healthcare, and government, where data breaches could lead to severe legal and financial consequences under GDPR and other regulations. Additionally, the lack of workarounds means organizations must prioritize patching to mitigate risk. The vulnerability could also be leveraged as a foothold for lateral movement within networks, amplifying its impact on operational continuity and data protection.

European organizations should immediately assess their deployment of VMware NSX, NSX-T, and VMware Cloud Foundation to identify affected versions. The primary mitigation is to apply the vendor-provided patches without delay, upgrading to the fixed versions listed by VMware (e.g., NSX 9.0.1.0, 4.2.2.2/4.2.3.1, 4.1.2.7, NSX-T 3.2.4.3). Since no workarounds exist, patching is critical. Organizations should also implement strict network segmentation and access controls to limit exposure of management interfaces to trusted networks only. Monitoring and alerting for unusual authentication attempts or brute-force patterns on NSX management portals should be enhanced. Employing multi-factor authentication (MFA) for administrative access can reduce the risk of credential compromise even if usernames are enumerated. Regularly reviewing and hardening password policies, including rate limiting and account lockout mechanisms, will further mitigate brute-force risks. Finally, conducting thorough audits of NSX logs and network traffic can help detect early signs of exploitation attempts.