Windows TDX.sys Privilege Escalation Flaw (CVE-2025-49659): Inside the Kernel's Buffer Over-read

The Windows kernel, a critical component underpinning millions of systems worldwide, faces a serious security threat from CVE-2025-49659. This vulnerability, residing within the Transport Driver Interface (TDI) Translation Driver (TDX.sys), exposes systems to potential privilege escalation attacks through a buffer over-read flaw. With a CVSS v3.1 base score of 7.8, this issue demands immediate attention from security teams.

Technical Information

The vulnerability originates from improper memory boundary validation within the TDX.sys driver, a legacy kernel-mode component designed to translate TDI requests to the newer Windows Filtering Platform (WFP). Although TDI has been deprecated since Windows Vista, it remains embedded in modern Windows versions for backward compatibility, inadvertently preserving a dangerous attack surface.

Specifically, the flaw allows an attacker with local access and valid credentials to issue maliciously crafted TDI requests, causing the driver to read beyond the allocated buffer. This unauthorized memory access can expose sensitive kernel data, including security tokens and function pointers. Attackers leveraging this vulnerability could manipulate these exposed kernel objects to escalate their privileges from a low-level user to SYSTEM-level access, bypassing all user-mode security controls.

The attack vector is strictly local, requiring no user interaction, and the exploitation complexity is notably low. This makes the vulnerability particularly concerning for scenarios where attackers have already gained initial access to a system and seek to elevate their privileges for further exploitation or lateral movement.

Patch Information

Microsoft has addressed the buffer over-read vulnerability in the Windows Transport Driver Interface (TDI) Translation Driver (TDX.sys) by releasing a security update as part of the July 2025 Patch Tuesday. This update modifies the TDX.sys driver to ensure proper bounds checking during memory operations, thereby preventing unauthorized memory access that could lead to privilege escalation. Users are strongly advised to apply this update promptly to secure their systems against potential exploitation.

Affected Systems and Versions

This vulnerability specifically impacts Windows systems utilizing the TDX.sys driver. While exact version ranges have not been explicitly detailed in available advisories, all current Windows versions maintaining backward compatibility with TDI are presumed vulnerable. Organizations should consider all Windows 10, Windows 11, and Windows Server editions potentially affected and prioritize patching accordingly.

Vendor Security History

Microsoft's security response to vulnerabilities in legacy components like TDI has historically been robust, though challenges persist due to the necessity of maintaining backward compatibility. Similar vulnerabilities have been identified in TDI-related components over recent years, underscoring the ongoing risk posed by these legacy subsystems. Microsoft's timely response to CVE-2025-49659, issuing a patch within their standard monthly update cycle, reflects their continued commitment to addressing security issues effectively.

References

Source: This report was created using AI

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