CVE-2026-20667 is a logic vulnerability identified in Apple’s macOS and other related operating systems, including watchOS, iOS, and iPadOS. The vulnerability stems from a flaw in the sandbox enforcement mechanism, where an application running with limited privileges can bypass the sandbox restrictions due to insufficient or improper validation checks. This sandbox escape allows the malicious app to gain elevated privileges beyond its intended scope, potentially leading to arbitrary code execution with high system privileges. The vulnerability is categorized under CWE-693, which relates to protection mechanism failures. Apple has released patches in macOS Tahoe 26.3, macOS Sonoma 14.8.4, macOS Sequoia 15.7.4, watchOS 26.3, iOS 26.3, and iPadOS 26.3 to address this issue by improving the logic checks that enforce sandbox boundaries. The CVSS v3.1 score of 8.8 reflects the high impact on confidentiality, integrity, and availability, with low attack complexity, requiring only limited privileges and no user interaction. Although no active exploitation has been reported, the vulnerability poses a significant risk because sandboxing is a critical security control designed to isolate applications and limit damage from compromised or malicious apps. Successful exploitation could allow attackers to bypass these controls, access sensitive data, modify system files, or disrupt system operations.

The impact of CVE-2026-20667 is substantial for organizations relying on Apple ecosystems, especially those using macOS and iOS devices in sensitive or high-security environments. A sandbox escape can lead to privilege escalation, allowing attackers to execute arbitrary code with elevated permissions, potentially compromising the entire system. This can result in unauthorized access to confidential information, installation of persistent malware, disruption of system availability, and undermining of system integrity. Enterprises that enforce strict app sandboxing to protect endpoints, such as financial institutions, government agencies, and healthcare providers, face increased risk of data breaches and operational disruption. The vulnerability also threatens developers and users of third-party applications that rely on sandboxing for security. Since exploitation requires local access with limited privileges, threat actors who gain initial footholds through phishing, social engineering, or physical access could leverage this flaw to deepen their control over targeted devices. The absence of known exploits in the wild currently reduces immediate risk but does not diminish the criticality of patching, as proof-of-concept exploits could emerge rapidly.

To mitigate CVE-2026-20667, organizations should immediately deploy the security updates released by Apple for macOS Tahoe 26.3, macOS Sonoma 14.8.4, macOS Sequoia 15.7.4, watchOS 26.3, iOS 26.3, and iPadOS 26.3. Beyond patching, organizations should implement strict application whitelisting to limit the execution of untrusted or unknown applications that could attempt sandbox escapes. Employ endpoint detection and response (EDR) solutions capable of monitoring for anomalous privilege escalation behaviors and sandbox violations. Restrict local user privileges to the minimum necessary to reduce the attack surface for local exploits. Conduct regular audits of installed applications and sandbox configurations to ensure compliance with security policies. For environments with high security requirements, consider deploying additional runtime protections such as system integrity protection (SIP) and mandatory access controls. Educate users about the risks of installing unverified applications and enforce policies to prevent unauthorized software installations. Finally, maintain robust incident response plans to quickly detect and respond to potential exploitation attempts.