CVE-2025-56499 is a security vulnerability identified in mihomo version 1.19.11 involving incorrect access control mechanisms. Specifically, authenticated attackers possessing low-level privileges can exploit this flaw to read arbitrary files with elevated privileges. The attack vector involves obtaining an external control key stored within the application's configuration file, which is insufficiently protected. By extracting this key, attackers can bypass intended access restrictions and access sensitive files that should be inaccessible to their privilege level. This vulnerability primarily compromises confidentiality by exposing potentially sensitive or critical data. Although the affected versions are not fully enumerated beyond v1.19.11, the lack of a CVSS score and absence of known exploits in the wild suggest it is a recently discovered issue. The vulnerability does not require user interaction beyond authentication, making it easier to exploit once credentials are obtained. The flaw highlights a failure in proper access control enforcement and secure storage of sensitive keys within the application environment.

For European organizations, this vulnerability poses a significant risk to data confidentiality and internal security. Attackers with low-level access could escalate their privileges to access sensitive configuration files, potentially exposing credentials, cryptographic keys, or other critical information. This could lead to further lateral movement within networks, data breaches, or disruption of services. Organizations in sectors such as finance, healthcare, and critical infrastructure that rely on mihomo or related software components are particularly vulnerable. The exposure of sensitive files could also result in compliance violations under GDPR and other data protection regulations, leading to legal and financial repercussions. The absence of known exploits currently reduces immediate risk but does not eliminate the threat, especially if attackers develop exploit code. The vulnerability's exploitation could undermine trust in affected systems and cause operational disruptions if sensitive configuration data is manipulated or leaked.

Organizations should immediately audit access controls on configuration files related to mihomo installations, ensuring that only authorized administrators have read permissions. Implement strict file system permissions and consider encrypting sensitive configuration files to prevent unauthorized reading. Monitor logs for unusual access patterns to configuration files or attempts to extract keys. Since no official patches are currently available, organizations should engage with mihomo vendors or maintainers to obtain updates or workarounds. Employ network segmentation to limit the impact of compromised low-level accounts and enforce the principle of least privilege across all user accounts. Conduct regular security assessments and penetration tests focusing on privilege escalation vectors. Additionally, implement multi-factor authentication to reduce the risk of credential compromise that could facilitate exploitation.