CVE-2026-87714 in Windows
Summary
by MITRE • 10/14/2026
Missing authorization in WebDAV allows an authorized attacker to bypass a security feature over a network.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability described constitutes a critical failure in access control mechanisms within the Web Distributed Authoring and Versioning protocol implementation, specifically classified under CWE-285 Improper Authorization. This flaw arises when the server fails to adequately verify whether an authenticated user possesses the necessary privileges to perform specific operations on requested resources. While the attacker is required to be authorized, meaning they possess valid credentials or a session token, the system incorrectly assumes that any logged-in user has unrestricted access to all available endpoints and functions within the WebDAV service. This misconfiguration effectively neutralizes security features designed to restrict sensitive administrative actions or data manipulation to specific roles, such as administrators or content managers, thereby allowing lower-privilege users to execute commands intended for higher-level accounts.
From a technical perspective, this issue typically stems from insufficient checks in the application logic handling HTTP methods like PUT, DELETE, MKCOL, or PROPFIND. When an authorized attacker sends requests with these methods targeting restricted directories or configuration files, the server processes them without validating if the user's role permits such actions. This bypass allows the attacker to modify file contents, delete critical data, create new directories for further exploitation, or retrieve sensitive metadata that should remain private. The absence of proper authorization checks means that the security boundary between different user roles is porous, enabling lateral movement within the application environment and potentially leading to full system compromise if combined with other vulnerabilities such as arbitrary file upload or server-side request forgery.
The operational impact of this vulnerability can be severe depending on the context in which the WebDAV service operates. If used for document management systems, attackers could alter official records, inject malicious scripts into documents, or exfiltrate confidential business intelligence by reading restricted files. In infrastructure contexts where WebDAV is used for backup storage or configuration management, an attacker could corrupt backups, delete essential system files, or plant web shells to maintain persistent access. This leads directly to breaches of confidentiality, integrity, and availability, which are the core tenets of information security. Furthermore, because the attack requires prior authentication, it often falls under post-exploitation scenarios where an initial foothold has already been gained through phishing, credential theft, or other entry points, making detection more difficult as the traffic appears legitimate from a network perspective.
To mitigate this risk, organizations must implement strict role-based access control (RBAC) policies that explicitly define which users can perform specific WebDAV operations. Developers should audit all endpoints to ensure that authorization checks are performed before any state-changing operation is executed, rather than relying solely on authentication tokens. It is also advisable to restrict the use of dangerous HTTP methods like DELETE and PUT to only those administrators who absolutely require them, potentially by configuring the web server or application firewall to block these verbs for non-administrative users. Additionally, implementing comprehensive logging and monitoring for WebDAV activities can help detect anomalous behavior indicative of such bypass attempts. Regular security assessments and penetration testing focused on access control flaws are essential to identify and remediate these gaps before they can be exploited in production environments. This approach aligns with ATT&CK techniques related to privilege escalation and unauthorized access, ensuring that defense-in-depth strategies effectively cover both network-level and application-layer vulnerabilities.