CVE-2025-43526 is a security vulnerability affecting Apple Safari on macOS systems that have Lockdown Mode enabled. Lockdown Mode is designed to provide a hardened security environment by restricting certain web APIs and features to reduce the attack surface. However, this vulnerability allows web content loaded via file URLs (i.e., local files opened in the browser) to access Web APIs that should be blocked under Lockdown Mode. This occurs due to insufficient URL validation, permitting local files to bypass intended API restrictions. The flaw could enable an attacker who can convince a user to open a crafted local file URL to execute scripts or access APIs that might expose sensitive information or perform unauthorized actions within the browser context. The vulnerability was addressed by Apple through improved URL validation in macOS Tahoe 26.2 and Safari 26.2, which enforce proper restrictions on file URL content in Lockdown Mode. There are no reports of active exploitation in the wild, but the vulnerability undermines a key security feature designed to protect high-risk users. The affected versions are unspecified, but users running earlier versions of macOS Tahoe and Safari prior to 26.2 remain vulnerable. The attack vector requires local file access and user interaction to open the malicious file URL, limiting remote exploitation but posing risks in scenarios involving malicious documents or compromised local files. This vulnerability highlights the importance of robust URL validation and the challenges of securing local content in hardened browser modes.

For European organizations, this vulnerability could lead to unauthorized access to sensitive data or execution of malicious scripts within Safari running in Lockdown Mode on macOS devices. Organizations that deploy Lockdown Mode as a security measure for high-risk users or executives may find this protection weakened, increasing the risk of targeted attacks via malicious local files or insider threats. The confidentiality and integrity of information accessed through Safari could be compromised, especially if attackers leverage crafted local files distributed via email, removable media, or insider vectors. Although the vulnerability does not enable remote code execution directly, the ability to bypass Lockdown Mode restrictions could facilitate further exploitation or data leakage. This is particularly concerning for sectors with stringent data protection requirements such as finance, healthcare, and government agencies in Europe. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially as attackers may develop techniques to leverage this flaw. Organizations relying on macOS and Safari for sensitive operations should consider this vulnerability a significant risk to their endpoint security posture.

European organizations should promptly update all macOS devices to macOS Tahoe 26.2 or later and Safari to version 26.2 or newer, where the vulnerability is fixed. IT administrators should audit and restrict the use of local file URLs in Safari, especially in environments where Lockdown Mode is enabled. Implement endpoint security controls that monitor and restrict the opening of untrusted local files or documents that could contain malicious file URLs. Educate users about the risks of opening unknown or unsolicited local files, particularly when using Lockdown Mode. Employ application whitelisting and file integrity monitoring to detect unauthorized or suspicious local files. Consider disabling or limiting Lockdown Mode temporarily if patching is delayed, while balancing the security trade-offs. Regularly review and update security policies related to browser usage and local file handling. Finally, monitor security advisories from Apple for any updates or additional mitigations related to this vulnerability.