CVE-2025-55696 Overview
CVE-2025-55696 is a time-of-check time-of-use (TOCTOU) race condition in the Windows NtQueryInformationToken function defined in ntifs.h. An authorized local attacker can exploit the race window to elevate privileges on affected Windows client and server systems. The flaw is classified under [CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition].
Microsoft addressed the issue in security updates referenced in the Microsoft Security Response Center advisory. The vulnerability affects a broad range of Windows 10, Windows 11, and Windows Server releases.
Critical Impact
Successful exploitation grants the attacker elevated privileges on the local system, enabling full compromise of confidentiality, integrity, and availability.
Affected Products
- Microsoft Windows 10 (1809, 21H2, 22H2)
- Microsoft Windows 11 (22H2, 23H2, 24H2, 25H2)
- Microsoft Windows Server 2019, 2022, 2022 23H2, and 2025
Discovery Timeline
- 2025-10-14 - CVE-2025-55696 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-55696
Vulnerability Analysis
The vulnerability resides in the kernel-mode NtQueryInformationToken routine, which returns information about an access token. A TOCTOU flaw exists between the point where the kernel validates token state and the point where it consumes that state. An attacker who can execute code locally and hold a token handle can manipulate token data between the check and use operations.
Because access tokens govern security context decisions, corrupting token queries in this window allows an attacker to influence privilege evaluation. The result is local elevation of privilege from a standard user context to a higher-privileged context.
Root Cause
The root cause is non-atomic access to token structure fields during the query operation. The kernel evaluates token attributes without holding an exclusive lock across the check and use phases. A concurrent thread can modify shared state between those phases, breaking the assumption that the validated data remains constant when it is subsequently read or acted upon.
Attack Vector
Exploitation requires local access with low privileges and no user interaction, though attack complexity is high because the attacker must reliably win a narrow timing race. A typical attack pattern uses two or more threads: one thread repeatedly issues NtQueryInformationToken calls while another thread mutates token-related state. When the race is won, the kernel processes attacker-controlled data as if it were validated, producing an elevation of privilege primitive.
No public proof-of-concept exploit is currently available, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. See the Microsoft advisory for CVE-2025-55696 for vendor-supplied technical context.
Detection Methods for CVE-2025-55696
Indicators of Compromise
- Unexpected processes running with SYSTEM or elevated integrity levels when spawned from standard user sessions.
- New services, scheduled tasks, or driver installations that follow anomalous token manipulation activity.
- Unusual crash dumps referencing NtQueryInformationToken, SeQueryInformationToken, or related token subsystem functions.
Detection Strategies
- Monitor Windows Security event IDs 4672 (special privileges assigned) and 4688 (process creation) for unexpected privilege escalations tied to non-administrative parent processes.
- Establish behavioral baselines for token manipulation APIs and alert on high-frequency, multi-threaded calls to token query routines from unprivileged processes.
- Correlate kernel-mode crashes and Event Tracing for Windows (ETW) anomalies with process lineage to identify race-condition exploitation attempts.
Monitoring Recommendations
- Enable audit policies for privilege use and process creation across all endpoints, and forward logs to a centralized analytics platform.
- Track processes that acquire SeDebugPrivilege, SeImpersonatePrivilege, or SeAssignPrimaryTokenPrivilege shortly after spawning from a standard user context.
- Review EDR telemetry for parent-child relationships where a low-privilege process yields a high-integrity child without a legitimate elevation path.
How to Mitigate CVE-2025-55696
Immediate Actions Required
- Apply the Microsoft security updates referenced in the MSRC advisory for CVE-2025-55696 across all affected Windows client and server systems.
- Prioritize patching on multi-user systems, terminal servers, virtual desktop infrastructure, and developer workstations where local code execution is common.
- Audit local user accounts and remove unnecessary interactive logon rights to reduce the population of potential local attackers.
Patch Information
Microsoft has released cumulative security updates addressing CVE-2025-55696 for all supported Windows 10, Windows 11, and Windows Server versions listed in the affected products. Consult the Microsoft update guide for the specific KB article and build numbers that apply to each operating system release.
Workarounds
- No official workaround has been published by Microsoft; applying the security update is the required remediation.
- Reduce exposure by restricting local logon rights, enforcing application allowlisting, and blocking execution of unsigned binaries from user-writable locations.
- Enable exploit protection and virtualization-based security (VBS) features such as Hypervisor-Protected Code Integrity (HVCI) to raise the cost of kernel exploitation.
# Verify installed update level on Windows to confirm patch presence
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# Query current build and revision for comparison against MSRC guidance
(Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion').CurrentBuild
(Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion').UBR
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
