CVE-2025-56499 is a vulnerability classified under CWE-284 (Improper Access Control) affecting mihomo version 1.19.11. The flaw arises because the application improperly restricts access to a sensitive external control key stored within its configuration file. Authenticated attackers with low-level privileges can exploit this weakness to read arbitrary files on the system, thereby gaining access to sensitive information that should be protected. The attack vector is network-based (AV:N), requiring low attack complexity (AC:L) and only low privileges (PR:L) without any user interaction (UI:N). The vulnerability affects confidentiality (C:H) but does not impact integrity or availability. Although no patches or known exploits are currently available, the exposure of critical configuration keys could facilitate further attacks or lateral movement within affected environments. The vulnerability is particularly concerning because it allows privilege escalation in terms of data access despite the attacker having limited initial permissions.

For European organizations, the primary impact is the unauthorized disclosure of sensitive information due to improper access control. This could include exposure of credentials, configuration secrets, or other critical data stored in the configuration files. Such data leaks could lead to further compromise, including unauthorized access to internal systems or services. Organizations in sectors with strict data protection regulations, such as finance, healthcare, and government, may face compliance risks and reputational damage if sensitive data is exposed. Additionally, attackers leveraging this vulnerability could move laterally within networks, increasing the scope of potential breaches. Since the vulnerability does not affect integrity or availability, direct disruption of services is unlikely, but the confidentiality breach alone poses significant risk.

To mitigate this vulnerability, organizations should first verify if they are running mihomo version 1.19.11 or earlier and prioritize upgrading to a patched version once available. In the absence of an official patch, restrict access to configuration files at the operating system level using strict file permissions to prevent unauthorized read access. Implement network segmentation and access controls to limit which authenticated users can reach the mihomo service. Employ monitoring and alerting for unusual file access patterns or privilege escalations. Conduct regular audits of user privileges to ensure that only necessary users have access to the application. Additionally, consider encrypting sensitive configuration data and rotating keys regularly to minimize exposure risk. Finally, maintain an incident response plan to quickly address any exploitation attempts.