CVE-2025-47996 Overview
CVE-2025-47996 is a local privilege escalation vulnerability in the Windows MBT (NetBIOS over TCP/IP) Transport driver. The flaw stems from an integer underflow (wrap or wraparound) condition that an authenticated local attacker can trigger to elevate privileges on affected systems. Microsoft published the advisory on July 8, 2025, covering supported client and server versions of Windows.
The vulnerability is categorized under [CWE-125] (Out-of-Bounds Read) and requires local access with low privileges. Successful exploitation compromises the confidentiality, integrity, and availability of the target system.
Critical Impact
An authorized local attacker can escalate privileges to SYSTEM by triggering an integer underflow in the Windows MBT Transport driver, gaining full control of the affected host.
Affected Products
- Microsoft Windows 10 (versions 1507, 1607, 1809, 21H2, 22H2)
- Microsoft Windows 11 (versions 22H2, 23H2, 24H2)
- Microsoft Windows Server 2008, 2012, 2016, 2019, 2022, 2022 23H2, and 2025
Discovery Timeline
- 2025-07-08 - CVE-2025-47996 published to NVD and Microsoft advisory released
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-47996
Vulnerability Analysis
The vulnerability resides in the Windows MBT Transport driver (mbt.sys), which implements NetBIOS over TCP/IP session and transport services. An integer underflow occurs when the driver processes input where an arithmetic operation on an unsigned value produces a result smaller than the minimum representable value, causing the value to wrap around to a very large number.
When this wrapped value is subsequently used as a size, offset, or loop bound, the driver reads memory outside the intended buffer boundary. This out-of-bounds condition, tracked as [CWE-125], can be leveraged in kernel context to corrupt adjacent structures or leak sensitive kernel memory that supports subsequent exploitation stages.
Because the flaw executes within a kernel-mode driver, successful exploitation results in code execution at the SYSTEM privilege level. This allows the attacker to bypass user-mode security boundaries, disable endpoint protections, and establish persistent access.
Root Cause
The root cause is an unchecked arithmetic operation on a length or offset field within the MBT Transport driver's packet or IOCTL handling path. When attacker-controlled input drives the operand values, the underflow condition wraps the result and produces an invalid memory access.
Attack Vector
Exploitation requires local access with authenticated, low-privileged credentials. The attacker interacts with the vulnerable driver from user mode, typically by issuing crafted requests that reach the affected code path. No user interaction is required beyond the attacker's own activity.
The vulnerability manifests in the MBT Transport driver's input handling logic. Consult the Microsoft CVE-2025-47996 Advisory for authoritative technical details.
Detection Methods for CVE-2025-47996
Indicators of Compromise
- Unexpected loading or interaction with mbt.sys from non-system processes running under low-privileged user accounts.
- Kernel bugcheck events (BSOD) referencing the MBT Transport driver, which may indicate failed exploitation attempts.
- Sudden token or privilege elevation events on user processes without a corresponding legitimate elevation workflow.
Detection Strategies
- Monitor Windows Event Log entries and WER (Windows Error Reporting) crash dumps that reference mbt.sys for anomalous frequency.
- Baseline legitimate NetBIOS over TCP/IP usage in the environment and alert on unusual IOCTL activity targeting the MBT driver.
- Use EDR behavioral rules to detect unexpected SYSTEM-level child processes spawned from standard user sessions.
Monitoring Recommendations
- Track patch compliance for the July 2025 Microsoft security updates across Windows endpoints and servers.
- Correlate kernel crash telemetry with authentication events to identify potential exploitation attempts against local accounts.
- Audit which user accounts have interactive logon rights on servers, as the attack requires local authenticated access.
How to Mitigate CVE-2025-47996
Immediate Actions Required
- Apply the July 2025 Microsoft security updates addressing CVE-2025-47996 to all affected Windows client and server systems.
- Prioritize patching multi-user systems, terminal servers, and jump hosts where multiple low-privileged accounts have local access.
- Review and reduce interactive logon rights for standard user accounts on sensitive servers.
Patch Information
Microsoft has published a security update for all affected Windows versions. Refer to the Microsoft CVE-2025-47996 Advisory for the specific KB articles corresponding to each Windows build. Install the updates through Windows Update, WSUS, or your enterprise patch management platform.
Workarounds
- Disable NetBIOS over TCP/IP on network adapters where the protocol is not required, which reduces exposure of the MBT Transport driver.
- Restrict local logon and remote desktop access to trusted administrative accounts until patches are deployed.
- Enforce application allowlisting to limit which binaries low-privileged users can execute on affected hosts.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
