CVE-2025-43526 is a critical security vulnerability identified in Apple Safari running on macOS systems with Lockdown Mode enabled. Lockdown Mode is designed to restrict certain Web APIs to reduce the attack surface against sophisticated threats. However, this vulnerability arises because web content opened via file URLs can bypass these restrictions due to insufficient URL validation. Specifically, Safari fails to properly validate file URL schemes, allowing local web content to access Web APIs that should be blocked under Lockdown Mode. This can enable an attacker to execute unauthorized actions, potentially leading to full compromise of the system's confidentiality, integrity, and availability. The vulnerability is exploitable remotely without requiring any privileges or user interaction, making it highly dangerous. Apple addressed this issue in macOS Tahoe 26.2 and Safari 26.2 by improving URL validation mechanisms to enforce the intended restrictions. The underlying weakness relates to CWE-601 (URL Redirection to Untrusted Site), indicating that improper handling of URLs leads to security bypass. While no known exploits are reported in the wild yet, the high CVSS score of 9.8 reflects the critical nature and ease of exploitation. Organizations relying on Safari with Lockdown Mode enabled must prioritize patching to prevent potential exploitation.

For European organizations, this vulnerability poses a significant risk, especially those in sectors with stringent security requirements such as finance, government, healthcare, and critical infrastructure. Exploitation could lead to unauthorized access to sensitive data, manipulation or corruption of information, and disruption of services. Since the vulnerability can be triggered without user interaction or privileges, it increases the likelihood of automated or remote attacks. Organizations enforcing Lockdown Mode to enhance security may have a false sense of protection, as this vulnerability undermines those restrictions. The impact extends to data confidentiality breaches, potential espionage, and operational downtime. Given the widespread use of macOS and Safari in professional environments across Europe, the vulnerability could affect a broad range of endpoints, increasing the attack surface. Additionally, regulatory compliance frameworks like GDPR may impose penalties if data breaches occur due to unpatched vulnerabilities.

1. Immediately update macOS to version Tahoe 26.2 or later and Safari to version 26.2 or later to apply the official patch from Apple. 2. Until patches are applied, restrict or monitor the use of file URLs in Safari, particularly in environments where Lockdown Mode is enabled. 3. Implement endpoint detection and response (EDR) solutions to identify suspicious local file access or unusual Web API usage patterns. 4. Educate users about the risks of opening local files with embedded web content, especially from untrusted sources. 5. Employ network-level controls to limit access to potentially malicious content and enforce strict content security policies. 6. Conduct regular vulnerability assessments and penetration testing focusing on macOS and Safari configurations. 7. Review and tighten application whitelisting and sandboxing policies to reduce the risk of local file exploitation. 8. Monitor security advisories from Apple and threat intelligence feeds for any emerging exploit activity related to this vulnerability.