A new vulnerability has emerged in the past few days that requires immediate attention. CVE-2025-21391, identified as an elevation of privilege vulnerability within Windows Storage, has been officially recognised by Microsoft. With an EPSS score indicating a rising threat level, understanding and addressing this vulnerability is essential for maintaining the security of your systems.
Technical Overview
CVE-2025-21391 has been classified under CWE-59 (an improper link resolution before file access). This vulnerability specifically affects Windows Storage, allowing attackers with local access to exploit the system. The vulnerability’s attack vector is local, meaning the attacker must have some level of access to the system, however, the complexity of the attack remains low making it relatively easy for attackers with low privileges to exploit the vulnerability without requiring any user interaction.
The main issue is the improper handling of file links, which can be manipulated by an attacker to delete targeted files.
EPSS and Threat Analysis
The Exploit Prediction Scoring System (EPSS) score for CVE-2025-21391 indicates a significant threat, with exploitation already detected in the wild. The functional exploit code maturity further underscores the urgency of addressing this vulnerability. With a CVSS score of 7.1, this vulnerability is categorised as important, emphasising the need for immediate remediation to prevent potential service disruptions.
Remediation Steps
To mitigate the risks associated with CVE-2025-21391, it is highly advised to follow the official guidance provided by Microsoft. Here are the steps you should take:
1. Apply Official Patches: Microsoft has released an official fix for this vulnerability. Ensure that all affected systems are updated with the latest security patches. You can find the update through Microsoft’s official security bulletin or Windows Update service.
2. Review and Monitor File Permissions: Regularly audit file permissions and access controls to minimise the risk of unauthorised file deletion.
3. Stay Informed: look out for any updates or additional guidance from Microsoft and other authoritative sources. Monitoring the EPSS score and related threat intelligence can provide insights into the evolving risk landscape. As this is a Zero-Day vulnerability, little information is still available on it.
By taking these steps, you can significantly reduce the risk posed by CVE-2025-21391 and safeguard your systems against potential exploitation. For further details, refer to Microsoft’s official advisory and continue prioritising security updates as part of your regular maintenance routine.