CVE-2025-49659 Overview
CVE-2025-49659 is a buffer over-read vulnerability in the Windows Transport Driver Interface Extension (TDX.sys) kernel driver. The flaw allows an authorized local attacker to elevate privileges on affected Microsoft Windows systems. The vulnerability is tracked as [CWE-126: Buffer Over-read] and impacts a broad range of Windows client and server releases, from Windows 10 1507 through Windows 11 24H2 and Windows Server 2008 through Windows Server 2025.
Microsoft assigned the vulnerability a CVSS 3.1 base score of 7.8 and released a security update through the Microsoft Security Response Center advisory.
Critical Impact
Successful exploitation grants SYSTEM-level privileges to a local attacker, enabling complete compromise 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-2025-49659 published to the National Vulnerability Database
- 2026-06-17 - Last updated in the NVD database
Technical Details for CVE-2025-49659
Vulnerability Analysis
The vulnerability resides in TDX.sys, the kernel-mode driver that implements the Transport Driver Interface Extension used by the Windows networking stack. A buffer over-read occurs when the driver reads beyond the bounds of an allocated buffer while processing attacker-influenced input. Because TDX.sys executes in kernel context, out-of-bounds reads can expose kernel memory or corrupt driver state used in subsequent privileged operations.
An authorized user on the local system can invoke the affected code path to trigger the over-read. The result is local elevation of privilege, giving the attacker the ability to run arbitrary code at kernel level and compromise confidentiality, integrity, and availability of the host.
Root Cause
The root cause is classified as [CWE-126: Buffer Over-read]. The driver fails to enforce correct length validation on a data structure before reading past its intended boundary. This missing boundary check permits an attacker-controlled request to cause the kernel to access adjacent memory contents that were not intended to be returned or processed.
Attack Vector
The attack vector is local and requires low-level privileges with no user interaction. An attacker who already has the ability to execute code on the target host, such as a standard user account or a foothold obtained through phishing or a separate initial-access vulnerability, can chain this flaw to escalate to SYSTEM. No public proof-of-concept exploit code has been published, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.
Microsoft has not released technical exploitation details. Refer to the Microsoft Security Update Guide for CVE-2025-49659 for vendor-provided information.
Detection Methods for CVE-2025-49659
Indicators of Compromise
- Unexpected process lineage where a non-administrative user process spawns a child running as NT AUTHORITY\SYSTEM.
- Kernel bug checks or crash dumps referencing TDX.sys on hosts that have not been patched.
- Loading of unsigned or unusual drivers immediately following suspicious local user activity.
Detection Strategies
- Monitor Windows Security event ID 4672 (special privileges assigned) for accounts that do not normally hold administrative rights.
- Correlate token manipulation and process-integrity-level changes with recent local logons from standard users.
- Track access to networking device objects associated with the TDI/TDX interface from unexpected user-mode processes.
Monitoring Recommendations
- Ingest Windows kernel telemetry, Sysmon process and image-load events, and WER crash reports into a centralized analytics platform for correlation.
- Establish behavioral baselines for privilege changes and driver interactions, and alert on deviations tied to non-administrative users.
- Prioritize alerts on hosts that have not received the July 2025 or later Patch Tuesday updates.
How to Mitigate CVE-2025-49659
Immediate Actions Required
- Apply the security update referenced in the Microsoft Security Update Guide for CVE-2025-49659 to all affected Windows client and server systems.
- Prioritize patching on multi-user hosts, jump servers, RDP session hosts, and virtual desktop infrastructure where local users are most likely to abuse the flaw.
- Restrict interactive and remote logon rights on servers to the minimum set of accounts required for operations.
Patch Information
Microsoft addressed CVE-2025-49659 through its standard security update channel. Administrators should install the cumulative update that corresponds to their Windows build via Windows Update, Windows Server Update Services (WSUS), Microsoft Update Catalog, or their patch management platform. Confirm remediation by verifying the updated TDX.sys file version referenced in the vendor advisory.
Workarounds
- No official workaround has been published by Microsoft; apply the vendor patch as the primary remediation.
- Enforce the principle of least privilege and remove unnecessary local user accounts on high-value servers to reduce the pool of potential attackers.
- Enable application control policies such as Windows Defender Application Control or AppLocker to limit execution of unauthorized binaries that could stage this exploit.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
