CVE-2025-40653 is a medium-severity vulnerability affecting all versions of the M3M Printer Server Web product. The vulnerability is classified under CWE-209, which involves the generation of error messages containing sensitive information. Specifically, this issue arises during the user authentication process where the application returns different error messages depending on whether a username exists or not. This discrepancy enables an attacker to perform user enumeration by analyzing the error responses, thereby confirming valid usernames. Once valid usernames are identified, an attacker can launch brute force attacks against these accounts to gain unauthorized access. The vulnerability is remotely exploitable over the network without requiring authentication or user interaction, as indicated by the CVSS vector (AV:N/AC:L/AT:N/UI:N/PR:N). The CVSS score of 6.9 reflects a medium severity level, primarily due to the potential for information disclosure and subsequent brute force attacks, although no direct impact on confidentiality, integrity, or availability is indicated beyond user enumeration. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability affects all versions of the M3M Printer Server Web, suggesting a systemic issue in how error messages are handled during authentication. This type of vulnerability is often overlooked but can be leveraged as a stepping stone for more severe attacks if combined with other weaknesses or poor password policies.

For European organizations using M3M Printer Server Web, this vulnerability poses a risk of unauthorized access through brute force attacks facilitated by user enumeration. While the immediate impact is limited to information disclosure about valid usernames, this can significantly aid attackers in compromising accounts, especially if weak or reused passwords are present. Compromise of printer server accounts could lead to unauthorized printing, interception of print jobs, or lateral movement within the network. Given that printer servers often have access to sensitive documents and may be integrated into corporate networks, exploitation could result in data leakage or disruption of business operations. Additionally, the vulnerability could be exploited as part of a larger attack chain targeting critical infrastructure or sensitive environments. The lack of authentication or user interaction requirements increases the risk, as attackers can scan and enumerate users remotely. European organizations with regulatory requirements around data protection (e.g., GDPR) must consider the potential for indirect data exposure and ensure that such vulnerabilities are addressed promptly to avoid compliance issues.

1. Implement uniform error messages during authentication to prevent user enumeration. All authentication failures should return the same generic error message regardless of whether the username exists. 2. Enforce strong password policies and account lockout mechanisms after a defined number of failed login attempts to mitigate brute force attacks. 3. Monitor authentication logs for unusual patterns indicative of enumeration or brute force attempts and trigger alerts. 4. Restrict access to the M3M Printer Server Web interface using network segmentation, VPNs, or IP whitelisting to limit exposure to trusted users only. 5. Apply web application firewalls (WAFs) with rules designed to detect and block enumeration and brute force activities. 6. Regularly update and patch the M3M Printer Server Web product once vendor patches become available. 7. Conduct security awareness training for administrators to recognize and respond to suspicious authentication activities. 8. Consider multi-factor authentication (MFA) for accessing the printer server web interface to add an additional layer of security.