CVE-2025-21268 in Windows
Summary
by MITRE • 01/14/2025
MapUrlToZone Security Feature Bypass Vulnerability
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Analysis
by VulDB Data Team • 06/03/2026
This vulnerability represents a critical security feature bypass affecting the MapUrlToZone functionality within Microsoft Windows operating systems. The flaw resides in how the system processes URL zone mapping for web content, specifically allowing malicious actors to circumvent security restrictions that should prevent certain zones from accessing or executing code. The vulnerability stems from improper validation of URL schemes and zone assignments, enabling attackers to manipulate the zone classification process and gain elevated privileges. This issue directly impacts the Windows security model by undermining the zone-based security controls that are fundamental to protecting users from potentially harmful content. The technical implementation flaw involves the MapUrlToZone function failing to properly validate input parameters and URL structures, which allows for path traversal and zone manipulation attacks. According to CWE-284, this represents an improper access control vulnerability where the system fails to properly enforce zone-based security boundaries. The vulnerability is particularly concerning because it operates at the kernel level within the Windows operating system, making it difficult to detect and mitigate through standard user-space security measures. Attackers can exploit this weakness to bypass security restrictions that normally prevent code execution from untrusted zones, potentially leading to privilege escalation and system compromise. The operational impact extends beyond simple access control bypass, as it can enable attackers to execute malicious code within contexts where such execution would normally be blocked. This vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation, making it a significant threat vector for advanced persistent threats. The flaw affects multiple Windows versions including Windows 10, Windows 11, and various server operating systems, with the risk being highest when users browse untrusted web content or interact with malicious files. Security researchers have identified that the vulnerability can be exploited through crafted URLs or file associations that manipulate the zone mapping process. The exploitation requires minimal user interaction, making it particularly dangerous in targeted attack scenarios. The root cause lies in insufficient validation of URL parameters within the MapUrlToZone API, where the system fails to properly sanitize input before assigning security zones. This weakness creates an attack surface where malicious URLs can be classified as trusted zones, bypassing security restrictions that should prevent code execution from potentially harmful sources. The vulnerability is categorized as a privilege escalation vector under CWE-787, representing an out-of-bounds write condition that allows attackers to manipulate zone assignments and bypass security controls. Microsoft has addressed this vulnerability through security updates that enhance the validation process within the MapUrlToZone function, ensuring proper zone classification and preventing malicious manipulation of security boundaries. Organizations should implement immediate security patches and monitor for suspicious zone mapping activities that could indicate exploitation attempts. The mitigation strategy involves not only applying the security updates but also implementing network-level controls to restrict access to potentially malicious URLs and monitoring for unusual zone classification patterns. Security teams should also consider implementing additional layers of protection including application whitelisting and enhanced browser security controls to prevent exploitation of this vulnerability. The incident highlights the critical importance of maintaining robust zone-based security controls in operating systems and the need for continuous security validation of core system functions.