CVE-2024-40842 is a vulnerability in Apple macOS, specifically fixed in the macOS Sequoia 15 release, that arises from insufficient validation of environment variables. This flaw allows a local application running with limited privileges (low privilege) to access sensitive user data without requiring user interaction. The vulnerability is classified under CWE-200, which involves exposure of sensitive information. The CVSS v3.1 score is 5.5 (medium severity), with the vector AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N indicating that the attack requires local access, low attack complexity, low privileges, no user interaction, and impacts confidentiality only. The vulnerability does not affect data integrity or system availability. The root cause is the improper handling and validation of environment variables, which can be manipulated or exploited by a local app to gain unauthorized access to sensitive data belonging to the user. Apple resolved this issue by enhancing the validation mechanisms for environment variables in macOS Sequoia 15. There are currently no known exploits in the wild, but the vulnerability poses a risk in environments where untrusted or malicious local applications may be present. This vulnerability is particularly relevant for multi-user systems or systems where apps from less trusted sources might be installed. Since the vulnerability requires local access and low privileges, remote exploitation is not feasible, limiting the attack surface primarily to local threat actors or compromised user accounts.

The primary impact of CVE-2024-40842 is the unauthorized disclosure of sensitive user data on affected macOS systems. Confidentiality is compromised as a local app can access data it should not be authorized to see. This could lead to leakage of personal information, credentials, or other sensitive content stored or accessible on the user's account. Although the vulnerability does not affect data integrity or system availability, the exposure of sensitive information can facilitate further attacks such as social engineering, privilege escalation, or lateral movement within an organization. Organizations with macOS devices, especially those in sectors handling sensitive or regulated data (e.g., finance, healthcare, government), face increased risk if local device security is weak or if users install untrusted applications. The requirement for local access and low privileges means that attackers must already have some foothold on the device, but the vulnerability lowers the barrier to accessing sensitive data once local access is obtained. This could be exploited by malicious insiders, compromised user accounts, or malware that gains local execution capabilities. The absence of known exploits in the wild reduces immediate risk but does not eliminate the threat, especially as attackers often develop exploits after public disclosure.

To mitigate CVE-2024-40842, organizations and users should promptly update to macOS Sequoia 15 or later, where the vulnerability has been fixed by improved validation of environment variables. Beyond patching, organizations should enforce strict application control policies to limit installation and execution of untrusted or unnecessary local applications, reducing the risk of local exploitation. Employ endpoint security solutions that monitor and restrict suspicious local process behavior and environment variable manipulations. Implement least privilege principles to minimize the number of users and applications with local access rights. Regularly audit and monitor local user accounts and installed applications for signs of compromise or unauthorized changes. Educate users about the risks of installing untrusted software and the importance of maintaining updated systems. For environments with shared or multi-user systems, consider additional isolation mechanisms such as sandboxing or containerization to limit data exposure between users. Finally, maintain robust logging and alerting to detect potential exploitation attempts involving environment variable abuse or unauthorized data access.