CVE-2025-26678 in Windows
Summary
by MITRE • 04/08/2025
Improper access control in Windows Defender Application Control (WDAC) allows an unauthorized attacker to bypass a security feature locally.
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Analysis
by VulDB Data Team • 07/09/2025
Windows Defender Application Control represents a critical security component within Microsoft's defense-in-depth strategy for endpoint protection, designed to prevent unauthorized applications from executing on Windows systems through strict policy enforcement mechanisms. This vulnerability stems from an improper access control implementation within WDAC that enables local attackers to circumvent the intended security controls. The flaw exists in the privilege escalation pathway where insufficient validation occurs during policy enforcement processes, allowing malicious actors with local system access to manipulate WDAC configurations and disable protective measures. The vulnerability specifically affects the authentication and authorization mechanisms that govern access to WDAC policy management interfaces and runtime enforcement components. Attackers can exploit this weakness to bypass application control policies that would normally prevent execution of malicious software, potentially leading to complete system compromise. The improper access control issue manifests when the system fails to properly validate user credentials or security contexts during critical WDAC operations, creating a privilege escalation vector that undermines the fundamental security model of the protection framework.
The technical implementation of this vulnerability resides in the core WDAC policy enforcement engine where access control lists and permission checks are inadequately implemented. When WDAC processes policy updates or enforcement decisions, the system fails to properly validate whether the requesting process possesses sufficient privileges to modify or bypass security controls. This weakness creates an attack surface where local users, whether legitimate or compromised, can manipulate WDAC settings through direct registry modifications or process injection techniques. The flaw specifically impacts the WDAC policy validation routines that should enforce strict access controls for policy management operations, but instead allow unauthorized modification of security parameters. According to CWE-284, this vulnerability represents an inadequate access control implementation that permits unauthorized access to protected resources. The attack vector typically involves local privilege escalation techniques where attackers leverage existing system access to modify WDAC configurations, potentially enabling the execution of unsigned or malicious code that would normally be blocked by the application control system.
The operational impact of this vulnerability extends beyond simple policy bypass scenarios, creating a significant risk to enterprise security postures and endpoint protection integrity. Organizations relying on WDAC for security enforcement face potential compromise when attackers exploit this access control flaw, as it allows complete bypass of application control policies that are meant to prevent unauthorized software execution. The vulnerability undermines the trust model that WDAC establishes, enabling attackers to escalate privileges and maintain persistence within the system while evading detection mechanisms. This weakness can be particularly dangerous in environments where WDAC is configured to enforce strict code integrity policies, as it provides a direct path for attackers to disable these protections entirely. The impact is amplified when considering that WDAC policies are often deployed as part of comprehensive security frameworks that include device control, driver signing enforcement, and application whitelisting. According to ATT&CK technique T1546.003, this vulnerability enables adversaries to modify system settings and disable security controls, while T1059.001 demonstrates how attackers can leverage these bypass capabilities to execute malicious code through various command and scripting interpreters.
Mitigation strategies for this vulnerability should focus on immediate patch management and access control hardening measures. Microsoft has released security updates that address the improper access control implementation in WDAC, requiring organizations to apply these patches promptly to restore proper security controls. System administrators should implement additional monitoring for unauthorized WDAC policy changes and establish baseline configurations that can detect modification attempts. The principle of least privilege should be enforced more strictly for WDAC management operations, ensuring that only authorized administrators possess the necessary permissions to modify security policies. Organizations should also implement network monitoring to detect suspicious WDAC configuration changes and establish automated alerting for policy modifications. Regular security assessments should verify that WDAC policies remain intact and that no unauthorized modifications have occurred. Additionally, implementing comprehensive audit logging for WDAC operations and establishing regular policy validation procedures can help identify exploitation attempts. The vulnerability highlights the importance of maintaining robust access control mechanisms and demonstrates how insufficient privilege validation in security-critical components can create significant attack vectors. Security teams should also consider implementing additional layers of protection such as integrity checking mechanisms and regular policy integrity verification to prevent exploitation of similar access control weaknesses.