CVE-2025-43526 is a critical security vulnerability discovered in Apple Safari running on macOS systems with Lockdown Mode enabled. Lockdown Mode is designed to provide enhanced security by restricting certain web APIs and functionalities to reduce attack surfaces. However, this vulnerability allows web content loaded via a file URL scheme (file://) to access Web APIs that should be restricted under Lockdown Mode. The root cause is insufficient URL validation, which fails to properly enforce the intended restrictions on local file URLs. This flaw could enable an attacker to craft malicious local files or trick users into opening such files, thereby bypassing Lockdown Mode's protections. Exploitation does not require user interaction or authentication, and the attack vector is network-based, making it remotely exploitable. The vulnerability impacts confidentiality, integrity, and availability, potentially allowing arbitrary code execution, data theft, or system compromise. Apple fixed the issue by improving URL validation in Safari 26.2 and macOS Tahoe 26.2. The vulnerability is tracked under CWE-601 (URL Redirection to Untrusted Site), indicating that improper URL handling is central to the issue. No known exploits are reported in the wild yet, but the high CVSS score (9.8) underscores the critical nature of this vulnerability and the urgency for remediation.

The impact of CVE-2025-43526 is severe for organizations worldwide using Apple Safari on macOS with Lockdown Mode enabled. Successful exploitation could allow attackers to bypass critical security restrictions, leading to unauthorized access to sensitive data, execution of arbitrary code, and potential full system compromise. This undermines the primary security benefits of Lockdown Mode, exposing users to advanced persistent threats and malware infections. Organizations relying on macOS devices for sensitive operations, including government agencies, financial institutions, healthcare providers, and enterprises with intellectual property, face heightened risks. The vulnerability's remote exploitability without user interaction increases the likelihood of automated or targeted attacks. Additionally, the ability to leverage local file URLs as an attack vector complicates detection and mitigation. The breach of confidentiality, integrity, and availability could result in data leaks, operational disruptions, reputational damage, and regulatory penalties. Given the widespread use of Safari and macOS in professional and consumer environments, the potential attack surface is extensive.

To mitigate CVE-2025-43526, organizations should: 1) Immediately update Apple Safari to version 26.2 or later and macOS to Tahoe 26.2 or later, where the vulnerability is fixed. 2) Enforce strict policies restricting the use of file URLs in web content, especially in environments where Lockdown Mode is enabled. 3) Implement endpoint security solutions capable of monitoring and blocking suspicious local file access or execution patterns. 4) Educate users about the risks of opening local files from untrusted sources, even when using Lockdown Mode. 5) Employ network-level controls to detect and prevent delivery of malicious local file URLs via phishing or other attack vectors. 6) Conduct regular security audits and penetration testing focused on local file handling and browser security configurations. 7) Consider disabling Lockdown Mode temporarily if patching is delayed, while balancing the security trade-offs. 8) Monitor security advisories and threat intelligence feeds for any emerging exploits targeting this vulnerability. These steps go beyond generic patching by emphasizing policy, user awareness, and layered detection to reduce exploitation likelihood.