CVE-2025-41252 Overview
VMware NSX contains a username enumeration vulnerability (CWE-203: Observable Discrepancy). An unauthenticated malicious actor may exploit this vulnerability to enumerate valid usernames on the system, potentially leading to unauthorized access attempts. This information disclosure weakness allows attackers to gather reconnaissance data that can be leveraged for subsequent credential-based attacks such as password spraying or brute force attempts.
Critical Impact
This vulnerability enables remote, unauthenticated attackers to discover valid usernames, significantly reducing the attack surface for credential-stuffing and brute force attacks against VMware NSX infrastructure.
Affected Products
- VMware NSX 9.x.x.x, 4.2.x, 4.1.x, 4.0.x
- NSX-T 3.x
- VMware Cloud Foundation (with NSX) 5.x, 4.5.x
Discovery Timeline
- Reported - Vulnerability reported by the National Security Agency
- 2025-09-29 - CVE CVE-2025-41252 published to NVD
- 2025-09-29 - Last updated in NVD database
Technical Details for CVE-2025-41252
Vulnerability Analysis
This vulnerability is classified as an information exposure issue stemming from observable discrepancies in the application's response behavior. The vulnerability allows attackers to distinguish between valid and invalid usernames based on differences in system responses, timing variations, or error messages returned during authentication attempts.
In the context of VMware NSX, which serves as a critical network virtualization and security platform, username enumeration poses significant risks. Attackers can systematically probe the authentication endpoint to build a list of valid accounts, which substantially increases the effectiveness of subsequent credential-based attacks. The network-accessible nature of this vulnerability means it can be exploited remotely without any prior authentication or user interaction.
Root Cause
The root cause lies in the application's authentication mechanism exhibiting observable differences when processing requests for valid versus invalid usernames (CWE-203: Observable Response Discrepancy). This could manifest through varied response times, distinct error messages, or different HTTP response codes that reveal whether a username exists in the system. Proper implementation should return identical responses regardless of username validity to prevent enumeration attacks.
Attack Vector
The attack can be executed remotely over the network without requiring authentication or user interaction. An attacker would typically send multiple authentication requests with different username values while monitoring the application's responses for discrepancies. By analyzing response patterns, timing differences, or error message variations, attackers can identify which usernames are valid. This enumerated list can then be used to conduct targeted password attacks, social engineering campaigns, or other follow-up attacks.
The vulnerability mechanism involves probing the NSX authentication interface to detect differences in responses between valid and invalid usernames. See the Broadcom Security Advisory for complete technical details.
Detection Methods for CVE-2025-41252
Indicators of Compromise
- Multiple failed authentication attempts from a single IP address targeting different usernames in rapid succession
- Unusual patterns of authentication requests with sequential or dictionary-based usernames
- Network traffic showing enumeration-style request patterns against NSX authentication endpoints
- Log entries indicating repeated authentication failures with low latency between attempts
Detection Strategies
- Implement rate limiting monitoring on authentication endpoints to detect enumeration attempts
- Configure alerts for authentication anomalies where multiple unique usernames are attempted from single sources
- Deploy network-based intrusion detection rules to identify username enumeration patterns
- Review NSX Manager audit logs for unusual authentication request volumes
Monitoring Recommendations
- Enable detailed authentication logging on all VMware NSX components
- Configure SIEM correlation rules to detect enumeration behavior patterns
- Monitor for authentication request spikes that may indicate active exploitation
- Establish baseline authentication patterns to improve anomaly detection accuracy
How to Mitigate CVE-2025-41252
Immediate Actions Required
- Apply the appropriate fixed version patches to all affected VMware NSX deployments
- Implement network segmentation to limit access to NSX management interfaces
- Enable account lockout policies to mitigate follow-up credential attacks
- Restrict management interface access to trusted networks and administrators only
Patch Information
VMware has released fixed versions to address this vulnerability:
- NSX 9.0.1.0
- NSX 4.2.2.2 / 4.2.3.1
- NSX 4.1.2.7
- NSX-T 3.2.4.3
- VMware Cloud Foundation: Apply async patch (KB88287)
Organizations should upgrade to the appropriate fixed version immediately. Refer to the Broadcom Security Advisory for detailed upgrade instructions.
Workarounds
- No vendor-provided workarounds are available for this vulnerability
- Implement network access controls to limit exposure of NSX management interfaces as a defense-in-depth measure
- Enable multi-factor authentication where supported to reduce risk from enumerated credentials
- Deploy web application firewalls with rate limiting to slow enumeration attempts
# Example: Restrict NSX management access to trusted networks via firewall rules
# Adjust IP ranges according to your environment
iptables -A INPUT -p tcp --dport 443 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
