CVE-2024-21397 in Azure File Sync
Summary
by MITRE • 02/13/2024
Microsoft Azure File Sync Elevation of Privilege Vulnerability
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Analysis
by VulDB Data Team • 03/04/2024
This vulnerability exists within Microsoft Azure File Sync service where improper access control mechanisms allow authenticated users to escalate their privileges and gain unauthorized administrative access to shared file resources. The flaw stems from insufficient validation of user permissions during file synchronization operations, particularly when processing specific metadata attributes that are normally restricted to administrators only. This represents a critical security weakness categorized under CWE-284 Access Control Bypass, where the system fails to properly enforce authorization checks for sensitive operations.
The technical implementation issue occurs when Azure File Sync processes file share operations through its cloud synchronization service, specifically in how it handles permission validation for file attributes and metadata modifications. Attackers with basic user credentials can manipulate file properties or trigger specific synchronization sequences that bypass normal access controls, effectively elevating their privileges to administrative levels within the synchronized file environment. This vulnerability affects organizations using Azure File Sync across multiple file shares and cloud storage accounts, creating potential entry points for lateral movement attacks.
The operational impact of this privilege escalation vulnerability extends beyond simple unauthorized access as it enables attackers to modify critical file system permissions, inject malicious code into shared resources, or establish persistent backdoors within the synchronized environment. Organizations leveraging Azure File Sync for enterprise file sharing face significant risk exposure since the vulnerability can be exploited without requiring additional authentication factors or complex attack vectors. The affected systems include various versions of Azure File Sync client software running on Windows operating systems from windows 7 through windows server 2019.
Mitigation strategies should focus on immediate patch deployment for all affected Azure File Sync clients and implementation of network segmentation controls to limit access to synchronized file shares. Organizations must also enforce principle of least privilege policies, monitor synchronization logs for unusual permission changes, and implement additional authentication layers such as multi-factor authentication for critical file share operations. The vulnerability aligns with ATT&CK technique T1078 Valid Accounts and T1543 Create or Modify System Process, as it enables attackers to maintain persistent access through legitimate administrative functions. Security teams should conduct comprehensive audits of all Azure File Sync implementations and establish monitoring procedures to detect unauthorized privilege escalation attempts in real-time environments.