Description

Time-of-check time-of-use (toctou) race condition in Windows Common Log File System Driver allows an authorized attacker to elevate privileges locally.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.0",
  "pubDate": "2026-08-11T17:18:23.910Z",
  "pubdate": "2026-08-11T17:18:23.910Z",
  "executiveSummary": "A time-of-check to time-of-use (TOCTOU) race condition vulnerability exists within the Windows Common Log File System Driver, impacting local Microsoft Windows environments.\nThis vulnerability allows an authorized local attacker to execute malicious code and achieve local elevation of privileges, potentially resulting in complete system compromise.\nThe flaw stems from a synchronization weakness during resource validation and usage within the kernel-mode driver, permitting an adversary with low-privileged access to manipulate shared resources or states between the validation phase and the execution phase.\nSuccessful exploitation requires local access and the ability to execute code on the target system, lowering the barrier for authenticated attackers seeking to escalate their privileges to administrative or SYSTEM levels.\nThe risk implications are severe, as an attacker who has gained standard user access can leverage this privilege escalation vector to bypass security boundaries, install persistent backdoors, access sensitive system data, or compromise the underlying operating system integrity.\nMitigation requires applying vendor-supplied security updates for the affected Windows Common Log File System Driver components and adhering to least-privilege principles to limit potential local attack surfaces.",
  "technicalDetails": "The vulnerability is a classic time-of-check to time-of-use (TOCTOU) race condition residing in the Windows Common Log File System Driver, which operates in kernel mode.\nThe root cause involves a synchronization flaw where the driver validates the security attributes, states, or contents of a resource at one point in time (time-of-check) but subsequently utilizes that same resource in an unsafe manner at a later point in time (time-of-use), without adequately locking or protecting the resource from concurrent modifications.\nAn authorized local attacker exploits this condition by initiating a sequence of asynchronous operations or multi-threaded requests directed at the vulnerable driver interface.\nDuring the window of vulnerability between the initial check and the final use, the attacker rapidly manipulates the shared object, file descriptor, or memory structure.\nBecause the kernel-mode driver trusts the initial validation and fails to re-verify the integrity or state of the resource immediately prior to the usage phase, the manipulated state is processed.\nThis discrepancy leads to unsafe memory handling, state corruption, or logic flaws within the kernel context.\nThe attack flow requires the adversary to be authenticated locally on the target machine with standard execution privileges.\nBy orchestrating precise timing loops or leveraging multiple concurrent threads, the attacker repeatedly interacts with the vulnerable driver functions until the race condition successfully triggers.\nUpon successful exploitation, the payload behavior manifests as arbitrary kernel-level read/write capabilities or control flow hijacking, which the attacker leverages to rewrite critical kernel structures.\nThe post-exploitation impact includes the successful local elevation of privileges, transitioning the execution context from a low-privileged user account to NT AUTHORITY\\SYSTEM, thereby granting total administrative control over the affected Windows operating system."
}