CVE-2025-49693 Overview
CVE-2025-49693 is a double free vulnerability [CWE-415] in the Microsoft Brokering File System that allows an authorized local attacker to elevate privileges on affected Windows systems. Successful exploitation grants an attacker the ability to execute code in a higher-privileged context, typically SYSTEM, from a standard user account.
The flaw affects current Windows 11 client releases and Windows Server 2022 23H2 and Windows Server 2025. Microsoft published the advisory on July 8, 2025.
Critical Impact
An authenticated local attacker can trigger a double free in the Brokering File System driver to elevate privileges, gaining full confidentiality, integrity, and availability impact on the host.
Affected Products
- Microsoft Windows 11 22H2, 23H2, and 24H2
- Microsoft Windows Server 2022 23H2
- Microsoft Windows Server 2025
Discovery Timeline
- 2025-07-08 - CVE-2025-49693 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-49693
Vulnerability Analysis
CVE-2025-49693 is a double free condition in the Microsoft Brokering File System (BFS), a Windows kernel-mode component that mediates file system access between processes and containers. A double free occurs when the same memory allocation is released twice, corrupting kernel heap metadata and enabling controlled reuse of freed structures.
BFS runs in the kernel and processes requests from user-mode callers. An attacker with local access and low-privilege authentication issues crafted requests that cause the driver to release the same object twice. The resulting heap corruption can be shaped into a write primitive that overwrites kernel structures such as process tokens.
Successful exploitation elevates the calling process to SYSTEM, providing full control over the operating system. The vulnerability requires no user interaction beyond running the exploit process.
Root Cause
The root cause is improper lifecycle management of a kernel object inside BFS. Under a specific request sequence, the driver's cleanup path frees an allocation that another code path also releases, producing a duplicate call to the memory manager for the same pointer. This condition is categorized under [CWE-415: Double Free].
Attack Vector
The attack vector is local. An attacker must already have the ability to execute code on the target system as an authenticated low-privilege user. From that context, the attacker invokes the BFS driver interface with a sequence of operations that triggers the duplicate free and then leverages the corrupted allocator state to hijack kernel execution or overwrite security tokens.
No verified public proof of concept is available. See the Microsoft CVE-2025-49693 Advisory for technical details.
Detection Methods for CVE-2025-49693
Indicators of Compromise
- Unexpected creation of processes running as NT AUTHORITY\SYSTEM that are children of standard-user processes.
- Kernel crashes or bug checks referencing the Brokering File System driver following user-mode activity from non-administrative accounts.
- New services, scheduled tasks, or persistence artifacts created immediately after suspicious low-privilege process activity.
Detection Strategies
- Monitor for process token elevation events where the parent process runs at medium integrity but the child runs at high or system integrity.
- Alert on Windows Error Reporting entries and Minidump files that name BFS-related kernel modules.
- Correlate local logons with subsequent SYSTEM-context command execution using EDR process ancestry telemetry.
Monitoring Recommendations
- Ingest Windows Security, Sysmon, and kernel crash telemetry into a centralized analytics platform for cross-event correlation.
- Track privilege escalation patterns per host over time to surface anomalous elevation from standard user accounts.
- Baseline expected callers of BFS interfaces so new or rare user-mode callers can be flagged for review.
How to Mitigate CVE-2025-49693
Immediate Actions Required
- Apply the Microsoft security update referenced in the Microsoft CVE-2025-49693 Advisory to all affected Windows 11 and Windows Server 2022 23H2 and 2025 systems.
- Prioritize patching on multi-user hosts, jump servers, and virtual desktop infrastructure where local attackers are more likely to gain a foothold.
- Audit local user accounts and remove unnecessary interactive logon rights to reduce the pool of potential attackers.
Patch Information
Microsoft released a security update addressing CVE-2025-49693. Refer to the Microsoft CVE-2025-49693 Advisory for the specific KB article and update packages corresponding to each affected Windows build.
Workarounds
- No official workaround is published by Microsoft; applying the security update is the required remediation.
- Restrict local and interactive logons on sensitive systems using Group Policy to limit exposure until patches are deployed.
- Enforce application allowlisting to prevent unauthorized binaries from executing at low privilege on unpatched hosts.
# Verify installed updates on a Windows host (PowerShell)
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 20
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
