CVE-2025-43521 is a vulnerability identified in Intel-based Apple macOS systems related to a downgrade issue that allows an application to bypass code-signing restrictions and access sensitive user data. The root cause is an insufficient enforcement of code-signing policies, which are critical for ensuring that only trusted and verified applications run with access to protected resources. This vulnerability is classified under CWE-347 (Improper Verification of Cryptographic Signature), indicating that the system fails to properly verify the authenticity or integrity of code signatures after a downgrade attack. The flaw requires local access and user interaction, meaning an attacker must convince a user to run a malicious app or perform an action that triggers the exploit. The CVSS v3.1 score of 5.5 reflects a medium severity, with a high confidentiality impact but no impact on integrity or availability. The vulnerability was addressed by Apple in macOS Tahoe 26.2 and macOS Sequoia 15.7.3 through enhanced code-signing restrictions that prevent downgrade attacks and ensure stricter validation of application signatures. No public exploits have been reported, but the potential for sensitive data exposure remains a concern, especially in environments where local device access is possible or where users may install untrusted applications.

For European organizations, this vulnerability poses a significant confidentiality risk as sensitive user data could be accessed by malicious applications exploiting the downgrade issue. The impact is particularly relevant for enterprises and government agencies that rely on Intel-based Macs for handling confidential or regulated data. Exposure could lead to data breaches, loss of intellectual property, or leakage of personal information, potentially violating GDPR and other privacy regulations. The requirement for local access and user interaction limits remote exploitation but does not eliminate risk in environments with shared or less controlled physical access. Organizations with remote or hybrid workforces using vulnerable macOS versions may face increased risk if endpoint security controls are insufficient. The medium severity rating suggests that while the threat is not critical, it warrants timely remediation to prevent escalation or combination with other attack vectors.

1. Apply the security updates provided by Apple immediately by upgrading to macOS Tahoe 26.2 or macOS Sequoia 15.7.3 or later versions. 2. Enforce strict application whitelisting policies using Apple’s built-in tools such as Gatekeeper and System Integrity Protection (SIP) to restrict execution to trusted and signed applications only. 3. Educate users about the risks of installing untrusted software and the importance of avoiding suspicious applications or links that could lead to local exploitation. 4. Implement endpoint detection and response (EDR) solutions capable of monitoring for anomalous local application behavior and potential code-signing bypass attempts. 5. Limit physical and local access to Mac systems, especially in shared or public environments, to reduce the risk of unauthorized app installation or execution. 6. Regularly audit installed applications and code-signing status to detect any unauthorized or downgraded binaries. 7. Integrate macOS security updates into organizational patch management workflows to ensure timely deployment across all affected devices.