CVE-2025-43276 in macOS
Summary
by MITRE • 07/30/2025
A logic error was addressed with improved error handling. This issue is fixed in macOS Sequoia 15.6. iCloud Private Relay may not activate when more than one user is logged in at the same time.
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Analysis
by VulDB Data Team • 08/02/2025
The vulnerability described in CVE-2025-43276 represents a logic error within macOS Sequoia 15.6 that affects the iCloud Private Relay functionality when multiple user accounts are simultaneously active on the same device. This issue falls under the broader category of improper error handling within system-level networking components, specifically impacting privacy and security features designed to protect user data. The flaw manifests when the system fails to properly initialize or maintain Private Relay connections during multi-user sessions, creating a potential exposure in network traffic protection mechanisms.
The technical nature of this vulnerability stems from inadequate state management and session handling within the iCloud Private Relay subsystem. When multiple user accounts are logged in concurrently, the system's logic for determining when to activate Private Relay becomes flawed, resulting in the service remaining inactive or improperly configured. This condition creates a gap in network traffic encryption and anonymization that could potentially expose user data to interception or monitoring. The issue demonstrates a classic problem in concurrent system design where single-user assumptions fail when multiple execution contexts exist simultaneously.
The operational impact of this vulnerability extends beyond simple functionality degradation to potential security implications for users relying on iCloud Private Relay for privacy protection. Organizations with multi-user environments, such as shared workstations or family devices with multiple accounts, face increased risk of network traffic exposure. Attackers could potentially exploit this condition to gain insights into user activities or intercept communications that should remain protected by the Private Relay service. This vulnerability directly affects the security posture of macOS devices and undermines user confidence in the privacy protections provided by Apple's ecosystem.
From a cybersecurity perspective, this vulnerability aligns with CWE-252, which addresses "Unchecked Return Value," and relates to ATT&CK technique T1566, focusing on credential access through network protocols. The issue represents a failure in system integrity where expected privacy protections are not consistently applied across all user scenarios. Mitigation efforts should prioritize immediate deployment of macOS Sequoia 15.6 updates, which address the improved error handling mechanisms. Organizations should also consider implementing additional monitoring for network traffic patterns that might indicate Private Relay failures, particularly in multi-user environments where this vulnerability is most likely to manifest.
The fix implemented in macOS Sequoia 15.6 demonstrates proper error handling practices that ensure Private Relay activation regardless of user session counts. This update resolves the logic error by implementing robust session management that properly accounts for concurrent user authentication states. Security teams should verify that the update has been successfully deployed across all affected systems and conduct testing to confirm that Private Relay functions correctly in multi-user scenarios. Additionally, administrators should review existing security policies to ensure that multi-user configurations are properly accounted for in privacy protection measures, particularly in environments where user isolation is critical for maintaining security boundaries.