CVE-2023-42940 is a medium-severity vulnerability affecting Apple macOS, specifically related to screen sharing functionality. The issue arises from a session rendering flaw where the system's session tracking does not correctly associate the content being shared with the user’s intended screen or window. As a result, a user who initiates screen sharing may unintentionally expose incorrect or unintended content to the viewers. This vulnerability is categorized under CWE-200, which pertains to information exposure. The flaw does not allow an attacker to directly execute code or disrupt system availability but can lead to unintended disclosure of sensitive or private information. The vulnerability requires local privileges (PR:L) and user interaction (UI:R), meaning the user must initiate screen sharing for the issue to manifest. The CVSS v3.1 base score is 5.7, reflecting a medium severity level, with a high impact on confidentiality but no impact on integrity or availability. The vulnerability was addressed by Apple in macOS Sonoma 14.2.1 through improved session tracking mechanisms that ensure the correct content is shared during screen sharing sessions. No known exploits are currently reported in the wild, and the affected macOS versions are unspecified, though the fix is available in the latest update. This vulnerability primarily affects users who frequently use screen sharing features, such as in remote work or collaboration scenarios, where accidental exposure of sensitive information could have privacy and security implications.

For European organizations, this vulnerability poses a risk primarily in environments where macOS devices are used for remote collaboration, presentations, or technical support involving screen sharing. The unintended sharing of incorrect content could lead to exposure of confidential business information, intellectual property, or personal data, potentially violating GDPR regulations and causing reputational damage. Sectors such as finance, legal, healthcare, and government agencies, which often handle sensitive data, are particularly at risk. While the vulnerability does not allow for system compromise or data manipulation, the confidentiality breach alone can have serious compliance and operational consequences. Since exploitation requires user interaction and local privileges, the risk is mitigated somewhat by user awareness and operational controls. However, in hybrid and remote work environments common in Europe, the risk of accidental data leakage increases. Organizations relying on macOS for critical communication should consider this vulnerability in their risk assessments and incident response planning.

European organizations should ensure all macOS devices are updated promptly to macOS Sonoma 14.2.1 or later, where the vulnerability is fixed. Beyond patching, organizations should implement strict policies and training around screen sharing practices, emphasizing verification of shared content before initiating sessions. Use of screen sharing tools with preview features or confirmation dialogs can reduce accidental exposure. Network-level controls such as restricting screen sharing to trusted endpoints and using secure VPNs can limit exposure. Additionally, endpoint monitoring solutions should be configured to detect unusual screen sharing activity. For highly sensitive environments, consider disabling native macOS screen sharing in favor of third-party solutions with enhanced security controls and audit capabilities. Regular audits of screen sharing logs and user behavior analytics can help identify potential misuse or accidental disclosures. Finally, incorporate this vulnerability into security awareness programs to educate users about the risks of unintended information exposure during collaboration.