CVE-2024-27837 is a vulnerability in Apple macOS that allows a local attacker to gain unauthorized access to Keychain items due to a downgrade issue involving code-signing restrictions. The Keychain is a secure storage system used by macOS to store passwords, certificates, and other sensitive credentials. The vulnerability arises because an attacker can bypass or downgrade the code-signing enforcement mechanisms that protect access to these Keychain items, thereby gaining access without proper authorization. This flaw is classified under CWE-280 (Improper Access Control) and affects unspecified versions of macOS prior to the fix. Apple addressed the issue in macOS Sonoma 14.5 by implementing additional code-signing restrictions to prevent downgrade attacks. The CVSS v3.1 base score is 7.7, reflecting high severity due to the vulnerability's impact on confidentiality and integrity, ease of local exploitation without privileges or user interaction, and the potential for unauthorized access to sensitive data. Although no exploits are currently known in the wild, the vulnerability poses a significant risk to any macOS user with local access to the system, including malicious insiders or attackers who have gained physical or remote local access. The vulnerability does not affect availability but compromises the confidentiality and integrity of stored credentials, which could lead to further system compromise or data breaches.

For European organizations, this vulnerability poses a significant threat to the confidentiality and integrity of sensitive credentials stored in macOS Keychains. Organizations in finance, healthcare, government, and critical infrastructure sectors that rely on macOS devices for secure credential storage are particularly at risk. Unauthorized access to Keychain items could lead to credential theft, lateral movement within networks, and escalation of privileges, potentially resulting in data breaches or disruption of services. The vulnerability's local nature means that attackers require some form of local access, which could be achieved through physical access, compromised user accounts, or malware with local execution capabilities. Given the widespread use of Apple devices in certain European countries and industries, the impact could be substantial if exploited. The absence of known exploits in the wild provides a window for organizations to patch and harden their systems before active exploitation occurs.

1. Immediately update all macOS systems to version Sonoma 14.5 or later, where the vulnerability is patched. 2. Enforce strict physical security controls to prevent unauthorized local access to macOS devices. 3. Limit local user accounts and privileges to reduce the risk of local exploitation. 4. Deploy endpoint detection and response (EDR) solutions capable of detecting suspicious local activities related to Keychain access. 5. Regularly audit and monitor access to Keychain items and system logs for anomalous behavior. 6. Educate users about the risks of local access and the importance of locking devices when unattended. 7. Consider implementing additional application whitelisting and code-signing enforcement policies to prevent downgrade attacks. 8. For high-security environments, consider using hardware-based security modules or multi-factor authentication to protect sensitive credentials beyond the Keychain.