CVE-2025-31218 is a vulnerability identified in Apple's macOS operating system, specifically addressed in macOS Sequoia 15.5. The vulnerability allows an application to observe the hostnames of new network connections initiated on the system. This issue stems from an information disclosure flaw categorized under CWE-200, where sensitive information—in this case, network connection hostnames—is exposed to unauthorized applications. The vulnerability does not require user interaction or privileges (AV:L/AC:L/PR:N/UI:N), meaning it can be exploited locally by any app without elevated permissions or user consent. The vulnerability impacts confidentiality (C:H), as it leaks potentially sensitive network metadata, but does not affect integrity or availability. The root cause was vulnerable code that allowed apps to monitor network connection hostnames, which Apple resolved by removing this code in the updated OS version. There are no known exploits in the wild at the time of publication, and the affected versions are unspecified but presumably all versions prior to macOS Sequoia 15.5. The CVSS score of 6.2 (medium severity) reflects the moderate risk posed by this information disclosure, given the local access requirement and the lack of impact on system integrity or availability.

For European organizations, this vulnerability could lead to unauthorized disclosure of network connection metadata, potentially exposing sensitive information about internal or external communications. This could aid attackers in reconnaissance activities, enabling them to map network interactions, identify critical services, or infer business relationships. While the vulnerability does not directly compromise system integrity or availability, the leakage of hostname information could facilitate targeted phishing, social engineering, or further exploitation by revealing communication patterns. Organizations with macOS endpoints, especially those handling sensitive or regulated data, may face increased risks of privacy breaches or intelligence gathering by malicious insiders or local attackers. The impact is more pronounced in environments where macOS devices are used for critical operations or where network confidentiality is paramount, such as in finance, healthcare, or government sectors.

European organizations should prioritize updating all macOS devices to version Sequoia 15.5 or later to eliminate the vulnerable code. Beyond patching, organizations should enforce strict application control policies to limit the installation and execution of untrusted or unnecessary applications, reducing the risk of local exploitation. Endpoint security solutions should be configured to monitor and alert on unusual application behaviors, including attempts to access network metadata. Network segmentation and the use of VPNs or encrypted DNS can help obscure hostname information from local apps. Additionally, organizations should conduct regular audits of installed software and user privileges to minimize the attack surface. For environments with high security requirements, consider deploying endpoint detection and response (EDR) tools capable of detecting suspicious local reconnaissance activities.