Microsoft Brokering File System Flaw (CVE-2025-49677): A Deep Look at Privilege Escalation Risks

Introduction

Local privilege escalation vulnerabilities often serve as critical pivot points for attackers seeking deeper system compromise. The recently disclosed CVE-2025-49677, a use-after-free flaw in Microsoft's Brokering File System, exemplifies such a risk. With a CVSS score of 7.0, this vulnerability allows attackers with local access to escalate privileges to SYSTEM-level authority, significantly increasing the potential damage from an initial compromise.

Technical Information

Vulnerability Mechanism

The root cause of CVE-2025-49677 lies in improper memory management within the Microsoft Brokering File System. Specifically, when file handles are closed, the system does not adequately clear pointers referencing freed memory. This oversight results in a use-after-free condition, where attackers can manipulate freed memory to overwrite kernel virtual function tables (v-tables).

Exploitation Method

Attackers exploit this vulnerability by:

Triggering the use-after-free condition through specially crafted file closure requests.
Manipulating the freed memory to corrupt kernel v-table pointers.
Redirecting execution flow to attacker-controlled shellcode, achieving arbitrary code execution at kernel level.

The deterministic memory layout of Windows kernel enhances the reliability of this exploit, reducing the complexity required for successful exploitation.

Affected Systems and Versions

Windows 11 Version 24H2 (all builds)
Windows Server 2025 (all builds)

Systems running these versions with the Brokering File System enabled are vulnerable.

Patch Information

Microsoft has addressed the 'use after free' vulnerability in the Microsoft Brokering File System (CVE-2025-49677) by releasing a security update as part of their July 2025 Patch Tuesday. This update modifies the way the Brokering File System handles objects in memory, ensuring that memory is properly managed and preventing unauthorized access. By applying this patch, systems are safeguarded against potential elevation of privilege attacks that could exploit this vulnerability. Users are strongly encouraged to install the update promptly to maintain system security.

Vendor Security History

Microsoft has repeatedly faced memory management vulnerabilities, particularly use-after-free flaws, in their kernel components. The recurrence of similar vulnerabilities indicates systemic challenges in Microsoft's approach to memory safety. However, Microsoft's prompt patch releases demonstrate their ongoing commitment to addressing security issues swiftly.

Threat Intelligence

Currently, there is no evidence of active exploitation of CVE-2025-49677. Nevertheless, given the public disclosure and detailed technical analysis available, the risk of exploitation attempts remains moderate. Security professionals should remain vigilant, closely monitoring kernel memory operations for anomalies.

References

Security teams are advised to promptly apply the available patches and maintain vigilance to mitigate the risks associated with this vulnerability.

Source: This report was created using AI

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