CVE-2025-21204 Overview
Improper link resolution before file access ('link following') in Windows Update Stack allows an authorized attacker to elevate privileges locally.
Critical Impact
This vulnerability could enable an attacker with local access to escalate privileges, potentially gaining full control over the affected systems.
Affected Products
- Microsoft Windows 10 1507
- Microsoft Windows 10 1607
- Microsoft Windows 10 1809
Discovery Timeline
- 2025-04-08 - CVE-2025-21204 published to NVD
- 2025-07-09 - Last updated in NVD database
Technical Details for CVE-2025-21204
Vulnerability Analysis
The vulnerability is due to improper link resolution before file access in the Windows Update Stack. When exploited, this allows an attacker with existing privileges to follow symbolic links to protected files, potentially leading to privilege escalation.
Root Cause
The root cause is the lack of proper validation for symbolic link resolution, allowing attackers to manipulate file access operations.
Attack Vector
An attacker needs local access to the vulnerable system and privileges to initiate file operations through the Windows Update Stack.
# Note: The following is a conceptual representation
# of potential exploitation rather than exact code.
ln -s /path/to/protected/file /path/to/symlink
echo "malicious command" > /path/to/symlink
Detection Methods for CVE-2025-21204
Indicators of Compromise
- Unexpected access to symbolic link files
- Unauthorized privilege modifications
- Unexplained modifications to system update files
Detection Strategies
Detecting symbolic link usage anomalies can reveal attempts to exploit this vulnerability. Monitoring file access patterns and alerting on changes to symbolic link locations are critical.
Monitoring Recommendations
Utilize SentinelOne's behavioral analysis to detect anomalous file system activities, specifically focusing on link resolution patterns and unauthorized access attempts.
How to Mitigate CVE-2025-21204
Immediate Actions Required
- Apply the latest security patches from Microsoft
- Deploy access controls to monitor and limit file operations
- Restrict local user privileges to the minimum necessary
Patch Information
Microsoft has released a patch addressing this vulnerability. Refer to the official Microsoft Security Response Center for patch details.
Workarounds
Employ File System ACLs (Access Control Lists) to restrict normal users from creating or modifying symbolic links.
# Configuration example: Set tighter permissions on
# directories containing symbolic links
chmod -R o-rwx /secure/directory
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
