CVE-2025-29970: Microsoft Brokering File System Privilege Escalation Vulnerability

Overview

The cybersecurity community is recent witness to a critical vulnerability in the Microsoft Brokering File System, known as CVE-2025-29970. This vulnerability, if exploited, allows an authorized attacker to escalate their privileges locally, potentially leading to system compromise or data leakage. Given the widespread usage of Microsoft systems across corporate, institutional, and individual platforms, this vulnerability has the potential to affect a large number of users, making its mitigation and resolution an imperative task.

Vulnerability Summary

CVE ID: CVE-2025-29970
Severity: High (7.8 CVSS Score)
Attack Vector: Local
Privileges Required: Low
User Interaction: None
Impact: System compromise or data leakage

Affected Products

Product | Affected Versions

Microsoft Brokering File System | All versions prior to the patch

How the Exploit Works

The vulnerability lies in the “use after free” flaw in the Microsoft Brokering File System. In essence, a “use after free” vulnerability occurs when a program continues to use a pointer after it has been freed. This can lead to program crashes and potentially allow an attacker to execute arbitrary code.
In the case of CVE-2025-29970, an attacker with local access can exploit this flaw to escalate their privileges. The exploit manipulates memory management, tricking the system into executing unauthorized commands with elevated privileges.

Conceptual Example Code

The following conceptual example demonstrates how an attacker might exploit this vulnerability:

#include <stdio.h>
#include <stdlib.h>
int main() {
char *ptr = malloc(10); // allocate memory
free(ptr); // free the memory
// "use after free" vulnerability
sprintf(ptr, "command with elevated privileges");
system(ptr); // execute the command
}

In this example, memory is allocated to the `ptr` pointer, then freed, and then used again to execute a command with elevated privileges.

Mitigation Guidance

To mitigate this vulnerability, it is advised that users apply the vendor patch as soon as it becomes available. In the meantime, users can employ a Web Application Firewall (WAF) or Intrusion Detection System (IDS) as temporary mitigation. Regular monitoring for any suspicious activity and maintaining up-to-date security measures are also recommended to protect against such vulnerabilities.