CVE-2025-41252 is a high-severity vulnerability affecting multiple versions of VMware NSX, including NSX 9.x.x.x, 4.2.x, 4.1.x, 4.0.x, NSX-T 3.x, and VMware Cloud Foundation with NSX 5.x and 4.5.x. The vulnerability is categorized under CWE-203, which pertains to observable discrepancies that enable username enumeration. Specifically, an unauthenticated remote attacker can exploit this flaw to enumerate valid usernames on the affected NSX management interfaces. This is achieved without requiring any prior authentication or user interaction, making the attack vector highly accessible. The vulnerability does not directly compromise system integrity or availability but poses a significant confidentiality risk by leaking valid usernames. Such information can be leveraged in subsequent targeted attacks, including brute force or credential stuffing, potentially leading to unauthorized access to critical network virtualization infrastructure. The CVSS v3.1 base score is 7.5 (High), reflecting the ease of exploitation (network, no privileges, no user interaction) and the impact on confidentiality (high). VMware has released fixed versions addressing this vulnerability, including 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 available, emphasizing the importance of timely patching. The vulnerability was responsibly disclosed by the National Security Agency and is currently not known to be exploited in the wild.

For European organizations, the impact of CVE-2025-41252 is significant due to the widespread adoption of VMware NSX for network virtualization and micro-segmentation in enterprise data centers and cloud environments. Username enumeration facilitates attackers in identifying valid user accounts, which can be used to launch targeted brute force or credential stuffing attacks, potentially compromising administrative accounts that control critical network infrastructure. Unauthorized access to NSX management components could lead to lateral movement within networks, data exfiltration, or disruption of network segmentation policies, undermining security postures. Given the reliance on NSX in sectors such as finance, healthcare, telecommunications, and government within Europe, exploitation could have cascading effects on confidentiality and operational security. The remote and unauthenticated nature of the vulnerability increases the risk profile, especially for organizations exposing NSX management interfaces to less trusted networks or the internet. Although no direct integrity or availability impacts are noted, the confidentiality breach alone can facilitate more severe attacks.

European organizations should prioritize immediate patching of affected VMware NSX and NSX-T deployments to the fixed versions specified 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, patch management is critical. Additionally, organizations should: 1) Restrict access to NSX management interfaces using network segmentation and firewall rules to limit exposure only to trusted administrative networks; 2) Implement strong multi-factor authentication (MFA) on all NSX user accounts to mitigate the risk of credential-based attacks following username enumeration; 3) Monitor authentication logs and network traffic for unusual login attempts or enumeration activity; 4) Employ intrusion detection/prevention systems (IDS/IPS) tuned to detect enumeration patterns; 5) Conduct regular security audits and penetration testing focusing on NSX components; 6) Educate administrators on recognizing and responding to suspicious activity related to NSX management access. These measures, combined with patching, will reduce the attack surface and improve detection and response capabilities.