CVE-2025-49694: Microsoft Brokering File System Null Pointer Dereference Enables Privilege Escalation

Introduction

A critical vulnerability, CVE-2025-49694, has emerged within Microsoft's Brokering File System (BFS), enabling authenticated local attackers to escalate privileges via a null pointer dereference. This flaw, rated 7.8 on the CVSS scale, poses significant risks to enterprise environments, particularly in scenarios involving insider threats or compromised accounts.

Technical Information

The vulnerability originates from improper null pointer validation within BFS. Specifically, when processing certain malformed file operation requests, BFS dereferences uninitialized or null pointers, causing controlled kernel memory corruption. This corruption can be leveraged by attackers to overwrite kernel structures or execute arbitrary code with elevated privileges.

Exploitation requires local access and authenticated user permissions, limiting the attack vector to insider threats or secondary exploitation post-initial compromise. The attack unfolds in three stages:

Triggering the Null Dereference: Attackers execute specially crafted file operations, bypassing input validation.
Memory Corruption: The null pointer dereference corrupts adjacent kernel memory, creating exploitable conditions.
Privilege Escalation: Attackers exploit corrupted memory to overwrite security tokens or execute kernel-mode payloads, achieving SYSTEM-level privileges.

Patch Information

Microsoft addressed this vulnerability in the July 2025 Patch Tuesday updates. Administrators should apply the following cumulative updates immediately:

Windows 11 22H2/23H2: KB5062570
Windows 11 24H2/Server 2025: KB5062553

Additional critical patches released include:

CVE-2025-47981: Heap-based buffer overflow in Windows SPNEGO Extended Negotiation (NEGOEX).
CVE-2025-49695 and CVE-2025-49696: Remote code execution vulnerabilities in Microsoft Office.
CVE-2025-49719: Information disclosure vulnerability in Microsoft SQL Server.
CVE-2025-49704: Remote code execution vulnerability in SharePoint.

Administrators must prioritize deploying these updates to secure their systems effectively.

Affected Systems and Versions

The vulnerability specifically affects:

Microsoft Windows 11 22H2/23H2 (prior to KB5062570)
Microsoft Windows 11 24H2/Server 2025 (prior to KB5062553)

Vendor Security History

Microsoft regularly addresses vulnerabilities through its monthly Patch Tuesday updates. Historically, the vendor demonstrates prompt response times, typically resolving critical issues within standard 30-day cycles. However, recurring memory safety vulnerabilities in Windows components highlight persistent security challenges.

References

Organizations are strongly advised to expedite patch deployment and implement recommended security measures to mitigate the risks associated with CVE-2025-49694.

Source: This report was created using AI

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