CVE-2026-44809: Windows Common Log File System Driver Elevation of Privilege Vulnerability

Synopsis

A use-after-free vulnerability in the Windows Common Log File System (CLFS) Driver allows a locally authenticated attacker to elevate privileges on affected Windows 11 and Windows Server 2025 systems. The attacker requires only a low-privilege local account and no interaction from any other user. Successful exploitation gives the attacker full control over the affected system, including read, write, and availability impact at high severity. Patched-image rebuilds at the fix versions are available on HarborGuard for environments running affected Windows builds.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityNot required

  The attacker needs an existing shell or process on the host; no network path to the target is required.

• AuthenticationRequired

  Any low-privilege local account is sufficient; the attacker does not need administrative rights to trigger the vulnerability.

• Victim interactionNot required

  No action from any other user or victim is required for the exploit to succeed.

• Attack complexityDetail

  The exploit is reliable and condition-free, with no race conditions or special environmental factors required.

Blast Radius

• A successful attacker reads protected files, credentials, and other high-confidentiality data stored on the host.
• The attacker writes or modifies kernel-level and user-space data, including security policy and audit records managed by the CLFS driver.
• The attacker gains the ability to crash or disable system services, including the host OS itself, causing a denial-of-service condition.
• Full privilege escalation to SYSTEM-level access is achievable, giving the attacker unrestricted control over the compromised Windows host.