CVE-2025-49694 Overview
CVE-2025-49694 is a null pointer dereference vulnerability in the Microsoft Brokering File System. An authenticated local attacker can exploit the flaw to elevate privileges on affected Windows systems. The vulnerability carries a CVSS 3.1 score of 7.8 and is categorized under [CWE-476]. Microsoft published the advisory on July 8, 2025, covering Windows 11 24H2, Windows Server 2022 23H2, and Windows Server 2025.
Exploitation requires local access and low privileges but no user interaction. Successful attacks yield high impact to confidentiality, integrity, and availability, effectively granting elevated privileges on the target host.
Critical Impact
A low-privileged local user can trigger a null pointer dereference in the Brokering File System driver to escalate privileges on Windows 11 24H2, Windows Server 2022 23H2, and Windows Server 2025.
Affected Products
- Microsoft Windows 11 24H2
- Microsoft Windows Server 2022 23H2
- Microsoft Windows Server 2025
Discovery Timeline
- 2025-07-08 - CVE-2025-49694 published to NVD and Microsoft released the security update
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-49694
Vulnerability Analysis
The vulnerability resides in the Microsoft Brokering File System (BFS), a component that mediates file system operations for brokered processes on Windows. The flaw is a null pointer dereference [CWE-476] triggered when the component processes crafted input from a local, authenticated caller. Rather than returning safely, execution reaches a code path that dereferences a pointer without validating that it holds a valid address.
Exploitation occurs entirely on the local host. An attacker who already has a foothold as a standard user can invoke the vulnerable interface and manipulate the resulting fault to achieve elevation of privilege. The end state is code execution in a higher-privileged security context, breaking the boundary between user-mode and privileged services.
Root Cause
The root cause is missing pointer validation inside the Brokering File System code path. A structure or handle expected to be initialized before use is instead null when accessed. In kernel or privileged service contexts, this condition can be shaped into a controllable primitive that leads to privilege escalation rather than a simple denial of service.
Attack Vector
The attack vector is local. The attacker must authenticate to the target system with at least standard user rights. No user interaction from a victim is required. Common preconditions include prior code execution via phishing, an initial access exploit, or credential compromise. Once local, the attacker calls the vulnerable BFS interface with parameters that force the null dereference and drive the follow-on privilege gain.
No verified code examples are available. Refer to the Microsoft Security Update CVE-2025-49694 for vendor-supplied technical details.
Detection Methods for CVE-2025-49694
Indicators of Compromise
- Unexpected System or SYSTEM-level child processes spawned from standard user sessions shortly after suspicious binary execution.
- Kernel or service crash events referencing the Brokering File System component in Windows Event Log or WER reports.
- New scheduled tasks, services, or registry autoruns created immediately after a local user logon.
Detection Strategies
- Hunt for anomalous token elevation events (Event ID 4672, 4673) tied to non-administrative source accounts.
- Correlate process creation telemetry (Sysmon Event ID 1) where a medium-integrity parent spawns a high or system integrity child.
- Monitor for repeated crashes of brokered file system services, which may indicate exploitation attempts that failed before succeeding.
Monitoring Recommendations
- Forward Windows Security, System, and Sysmon logs to a centralized analytics platform for behavioral correlation.
- Baseline privilege escalation activity per host and alert on deviations from normal user-to-SYSTEM transitions.
- Track patch state of Windows 11 24H2, Windows Server 2022 23H2, and Windows Server 2025 endpoints to identify unpatched hosts most at risk.
How to Mitigate CVE-2025-49694
Immediate Actions Required
- Apply the Microsoft security update referenced in the Microsoft Security Update CVE-2025-49694 advisory to all affected Windows 11 24H2, Windows Server 2022 23H2, and Windows Server 2025 systems.
- Prioritize patching on multi-user hosts, jump servers, and virtual desktop infrastructure where local users routinely operate.
- Audit local accounts and remove unnecessary interactive logon rights to reduce the pool of potential attackers.
Patch Information
Microsoft addressed CVE-2025-49694 through the July 2025 security update cycle. Administrators should deploy the cumulative update for their specific Windows build as listed in the vendor advisory. Confirm installation by validating the updated build number and reviewing WSUS, Intune, or Configuration Manager compliance reports.
Workarounds
- No official vendor workaround is published; apply the security update as the primary remediation.
- Restrict local logon rights and enforce least privilege to limit which accounts can invoke the vulnerable interface.
- Enable application allowlisting (Windows Defender Application Control or AppLocker) to block untrusted binaries that could stage local exploitation.
# Verify patch status on a Windows host
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 20
# Query current OS build to confirm it matches the patched build listed in MSRC
[System.Environment]::OSVersion.Version
(Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion').UBR
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
