Critical Microsoft Vulnerability CVE-2026-46102 Under Active Exploitation

Microsoft has released emergency security updates to address CVE-2026-46102, a critical vulnerability under active exploitation. Attackers can exploit this flaw to gain system privileges without authentication.

The vulnerability affects multiple Microsoft products including Windows Server 2022, Windows 11, and Azure services. CVSS scores range from 8.1 to 9.8 depending on the affected product and configuration.

"This vulnerability poses an immediate threat to unpatched systems," stated Microsoft's security advisory. "Organizations should prioritize deployment of these security updates."

Technical Details

CVE-2026-46102 is a privilege escalation vulnerability in the Windows Common Log File System (CLFS) driver. Attackers can exploit a race condition in the CLFS handling to corrupt kernel memory and execute arbitrary code with SYSTEM privileges.

The vulnerability exists due to improper validation of input parameters when processing specially crafted CLFS container files. Successful exploitation could allow attackers to completely compromise affected systems.

Affected Products

• Windows 10 Version 21H2 and later
• Windows 11 Version 22H2 and later
• Windows Server 2022
• Windows Server 2019
• Azure Stack HCI
• Azure IoT Edge

Mitigation Steps

Microsoft has released security updates for all affected products. Organizations should:

1. Apply the latest security updates immediately
2. Restart systems after installation
3. Verify patch deployment using Microsoft's Update Compliance
4. Monitor for exploitation attempts

Workarounds

For systems that cannot be patched immediately, Microsoft recommends:

• Disable the CLFS driver via Group Policy
• Implement application control policies to prevent unauthorized CLFS access
• Deploy network segmentation to limit exposure

Timeline

• Vulnerability discovered: December 2025
• Patch release: January 14, 2026
• Active exploitation detected: January 15, 2026

Organizations can download the security updates from the Microsoft Security Update Guide or through Windows Update. Additional technical details are available in the official advisory.

CISA has added this vulnerability to its Known Exploited Vulnerabilities Catalog, requiring federal agencies to patch within 14 days. Private sector organizations are strongly encouraged to follow this timeline.