CVE-2025-43521 is a vulnerability identified in Intel-based Apple macOS systems that stems from a downgrade issue related to code-signing enforcement. Code-signing is a security mechanism that ensures only trusted and verified applications run on the system. This vulnerability allows an application to bypass these restrictions by exploiting a downgrade flaw, which effectively reduces the security checks applied to the app. As a result, a malicious or compromised app could gain unauthorized access to sensitive user data without requiring elevated privileges, although user interaction is necessary to trigger the exploit. The vulnerability affects macOS versions prior to Sequoia 15.7.3 and Tahoe 26.2, where Apple introduced additional code-signing restrictions to close this security gap. The CVSS v3.1 score of 5.5 reflects a medium severity level, with an attack vector limited to local access (AV:L), low attack complexity (AC:L), no privileges required (PR:N), but requiring user interaction (UI:R). The impact is primarily on confidentiality (C:H), with no impact on integrity or availability. The underlying weakness is categorized under CWE-347, which relates to improper verification of cryptographic signatures. No public exploits have been reported so far, indicating that while the vulnerability is significant, it is not yet actively exploited in the wild.

The primary impact of CVE-2025-43521 is unauthorized disclosure of sensitive user data on affected Intel-based macOS systems. Since the vulnerability allows an app to bypass code-signing restrictions, attackers could potentially access personal files, credentials, or other confidential information stored on the device. This could lead to privacy breaches, identity theft, or further compromise if sensitive data is used for lateral movement or social engineering. The requirement for local access and user interaction limits the attack surface, reducing the likelihood of widespread remote exploitation. However, organizations with Intel-based Macs, especially those in sensitive sectors such as finance, healthcare, or government, could face targeted attacks aiming to extract valuable information. The vulnerability does not affect system integrity or availability, so it does not directly enable system takeover or denial of service. Nonetheless, the confidentiality breach alone can have serious consequences for individuals and enterprises relying on macOS devices for secure operations.

To mitigate CVE-2025-43521, organizations and users should immediately update affected Intel-based macOS systems to macOS Sequoia 15.7.3, macOS Tahoe 26.2, or later versions where the vulnerability is patched. Since the issue involves code-signing enforcement, ensure that all applications installed are from trusted sources and properly signed by Apple or verified developers. Employ endpoint protection solutions that monitor application behavior and detect anomalous access to sensitive data. Restrict local access to macOS devices through strong physical security controls and user authentication policies to reduce the risk of malicious app installation. Educate users to avoid interacting with untrusted applications or links that could trigger the exploit. Additionally, implement application whitelisting and leverage macOS security features like System Integrity Protection (SIP) and Gatekeeper to enforce stricter execution policies. Regularly audit installed software and system logs for suspicious activity related to code-signing bypass attempts. Finally, maintain a robust patch management process to ensure timely deployment of security updates.