CVE-2026-49162 Overview
CVE-2026-49162 is a use-after-free vulnerability [CWE-416] in the Microsoft Brokering File System. An authorized local attacker can exploit the flaw to elevate privileges on affected Windows systems. Successful exploitation grants high impact to confidentiality, integrity, and availability on the target host.
The issue affects Windows 11 versions 24H2, 25H2, and 26H1 across x64 and arm64 architectures, as well as Windows Server 2025. Microsoft published details through the Microsoft Security Response Center (MSRC) update guide.
Critical Impact
A local, authenticated attacker who wins a memory-reuse race in the Brokering File System can execute code in a higher-privileged context, leading to full system compromise.
Affected Products
- Microsoft Windows 11 24H2 (x64, arm64)
- Microsoft Windows 11 25H2 (x64, arm64) and Windows 11 26H1 (x64, arm64)
- Microsoft Windows Server 2025
Discovery Timeline
- 2026-07-14 - CVE-2026-49162 published to NVD
- 2026-07-16 - Last updated in NVD database
Technical Details for CVE-2026-49162
Vulnerability Analysis
The Microsoft Brokering File System (BFS) mediates file access between application containers and the underlying Windows file system. The component tracks broker objects that represent handles, sessions, and access tokens between the client process and the kernel.
CVE-2026-49162 arises when the component frees an internal object while another code path retains a reference to the same allocation. Subsequent operations dereference the freed memory, giving the attacker control over object contents at reuse time. The attacker can shape the reused allocation to redirect execution or manipulate privileged data structures.
Exploitation requires local access and low privileges, but the attack complexity is high because the attacker must reliably win a race against the free operation. When achieved, the attacker gains code execution in the context of the Brokering File System, which runs with elevated rights on the host.
Root Cause
The root cause is improper lifetime management of a heap-allocated broker object. A reference is released along one code path while a second path continues to use the pointer without validating that the object is still live. This is a classic use-after-free pattern tracked under [CWE-416].
Attack Vector
An attacker first needs a local account on the target Windows 11 or Windows Server 2025 host. The attacker triggers a specific sequence of Brokering File System requests that force concurrent allocation, release, and re-use of the vulnerable object. Winning the race yields controlled memory contents inside a privileged process, enabling privilege elevation to SYSTEM.
No public proof-of-concept, exploit code, or in-the-wild activity has been reported. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. Refer to the Microsoft Security Update for CVE-2026-49162 for vendor guidance.
Detection Methods for CVE-2026-49162
Indicators of Compromise
- Unexpected crashes or Watson error reports referencing the Brokering File System driver or associated user-mode broker processes.
- New SYSTEM-context child processes spawned from low-privileged parent processes shortly after suspicious BFS activity.
- Anomalous handle open patterns from sandboxed or AppContainer processes touching broker file objects at high frequency.
Detection Strategies
- Hunt for local processes that transition from a standard-user token to a SYSTEM token without a documented service or scheduled task explaining the change.
- Correlate application crash telemetry involving BFS components with subsequent privileged process creations on the same host.
- Alert on kernel or user-mode faults inside broker modules that repeat across multiple endpoints, indicating exploitation attempts against the same primitive.
Monitoring Recommendations
- Forward Windows Application, System, and WER crash logs to a central analytics store and baseline BFS-related faults per host.
- Enable Windows Defender Application Control or Attack Surface Reduction telemetry to record process token elevations and unusual parent-child chains.
- Track patch compliance for Windows 11 24H2, 25H2, 26H1, and Windows Server 2025 so that unpatched systems surface quickly in vulnerability dashboards.
How to Mitigate CVE-2026-49162
Immediate Actions Required
- Apply the Microsoft security update referenced in the MSRC advisory for CVE-2026-49162 to all affected Windows 11 and Windows Server 2025 hosts.
- Prioritize patching for multi-user systems, jump servers, and developer workstations where local accounts can be leveraged for elevation.
- Audit local account membership and remove unnecessary interactive logon rights until patches are deployed.
Patch Information
Microsoft has issued a security update for CVE-2026-49162 through the standard Windows Update channel. The update addresses the object lifetime handling in the Brokering File System for Windows 11 24H2, 25H2, and 26H1 (x64 and arm64) and Windows Server 2025. Consult the Microsoft Security Update Guide for the specific KB article and build numbers applicable to each SKU.
Workarounds
- No official workaround has been published by Microsoft. Patch deployment is the supported remediation.
- Reduce exposure by restricting local logon and remote desktop access to trusted administrators until updates are installed.
- Enforce application allowlisting to limit unknown binaries from exercising the Brokering File System interface from low-privileged contexts.
# Verify installed cumulative update on affected hosts
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# Trigger Windows Update scan and install available security updates
UsoClient StartScan
UsoClient StartInstall
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
