CVE-2024-27837 is a vulnerability in Apple macOS identified as a downgrade issue related to code-signing restrictions that affects the security of Keychain items. The Keychain is a secure storage system used by macOS to hold sensitive information such as passwords, certificates, and cryptographic keys. The vulnerability allows a local attacker—someone with physical or remote local access but no elevated privileges—to bypass certain code-signing enforcement mechanisms by exploiting a downgrade flaw. This bypass enables unauthorized access to Keychain items, compromising confidentiality and integrity of stored secrets. The issue was addressed by Apple in macOS Sonoma 14.5 through enhanced code-signing restrictions that prevent the downgrade attack vector. The CVSS v3.1 score of 7.7 indicates a high-severity vulnerability with low attack complexity, no privileges required, and no user interaction needed. Although no exploits are currently known in the wild, the vulnerability poses a significant risk because it enables attackers to extract sensitive credentials locally, which can then be used for further attacks such as privilege escalation, lateral movement, or data exfiltration. The vulnerability is categorized under CWE-280 (Improper Restriction of Operations within the Bounds of a Memory Buffer), highlighting the underlying issue with downgrade enforcement. Since the affected versions are unspecified but fixed in Sonoma 14.5, all prior macOS versions remain vulnerable until patched. This vulnerability is particularly concerning for environments where macOS devices are used to store critical credentials or cryptographic keys, including enterprise and government sectors.

For European organizations, the impact of CVE-2024-27837 is significant due to the widespread use of Apple macOS devices in business, government, and critical infrastructure sectors. Successful exploitation allows a local attacker to access sensitive Keychain items, potentially exposing passwords, private keys, and certificates used for authentication and encryption. This can lead to unauthorized access to corporate networks, confidential data breaches, and compromise of secure communications. The confidentiality and integrity of sensitive information are directly threatened, increasing the risk of identity theft, espionage, and lateral movement within networks. Although availability is not affected, the breach of credentials can facilitate further attacks that disrupt operations. Organizations with remote or shared workstation environments, or those with insufficient physical security controls, are at higher risk. The lack of required privileges or user interaction lowers the barrier for exploitation by insiders or attackers who gain local access through other means. Given the high CVSS score and the critical nature of Keychain data, European entities must prioritize patching and monitoring to mitigate potential damage.

To mitigate CVE-2024-27837, European organizations should: 1) Immediately update all macOS devices to version Sonoma 14.5 or later, where the vulnerability is fixed. 2) Enforce strict endpoint security policies to limit local access to authorized personnel only, including physical security controls and user account restrictions. 3) Implement robust monitoring and logging of local access attempts and unusual Keychain access patterns to detect potential exploitation. 4) Use Mobile Device Management (MDM) solutions to ensure compliance with patching and security configurations across all Apple devices. 5) Educate users about the risks of local device compromise and enforce strong authentication mechanisms such as biometrics or multi-factor authentication to reduce unauthorized local access. 6) Review and minimize the number of sensitive credentials stored in the Keychain, rotating keys and passwords regularly. 7) Consider additional encryption or hardware security modules for highly sensitive keys to add layers of protection beyond the Keychain. 8) Conduct regular security audits and penetration testing focused on local privilege escalation and credential access scenarios to identify residual risks.