CVE-2025-29970 Overview
CVE-2025-29970 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. Microsoft published the advisory on May 13, 2025, and the issue affects supported builds of Windows 11 24H2, Windows Server 2022 23H2, and Windows Server 2025.
Successful exploitation grants high impact to confidentiality, integrity, and availability, allowing an attacker with low-privilege local access to achieve elevated code execution. No public proof-of-concept exists, and CISA has not added the CVE to the Known Exploited Vulnerabilities catalog.
Critical Impact
A local, authenticated attacker can elevate privileges on unpatched Windows 11 24H2, Windows Server 2022 23H2, and Windows Server 2025 systems by triggering a use-after-free in the Brokering File System.
Affected Products
- Microsoft Windows 11 24H2 (x64 and ARM64)
- Microsoft Windows Server 2022 23H2
- Microsoft Windows Server 2025
Discovery Timeline
- 2025-05-13 - Microsoft publishes advisory and releases security patch
- 2025-05-13 - CVE-2025-29970 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-29970
Vulnerability Analysis
The vulnerability resides in the Microsoft Brokering File System, a Windows component that brokers file operations between processes with differing trust levels. A use-after-free condition [CWE-416] occurs when the component references memory that has already been released. An authorized local attacker can manipulate object lifecycle handling to trigger the dangling reference.
Once the freed memory is reallocated with attacker-controlled contents, the subsequent dereference can hijack execution flow inside a higher-privileged context. This allows a standard user to transition from low-privilege code execution to SYSTEM-level operations. The advisory characterizes the flaw as an elevation of privilege class issue rather than remote code execution.
Root Cause
The root cause is improper object lifetime management within the Brokering File System driver code. When a file brokering object is released, at least one code path retains a stale pointer instead of nullifying or reference-counting the object. Reuse of the freed allocation while the stale pointer is still active yields the exploitable primitive.
Attack Vector
Exploitation requires local access and low-privilege authentication on the target system. The attacker does not need user interaction and can drive the vulnerable code path through crafted requests to the brokering service. The scope remains unchanged, meaning exploitation elevates privileges within the same security authority rather than crossing trust boundaries such as VM escape.
No verified public exploit code is available for CVE-2025-29970. Refer to the Microsoft Security Update Guide for CVE-2025-29970 for authoritative technical details.
Detection Methods for CVE-2025-29970
Indicators of Compromise
- Unexpected crashes or exceptions in processes hosting the Brokering File System component, particularly access violations tied to freed memory regions.
- Standard user processes that suddenly spawn child processes running as SYSTEM without a legitimate elevation prompt or scheduled task origin.
- Unusual handle activity or repeated open/close cycles against brokered file objects from non-administrative accounts.
Detection Strategies
- Hunt for local privilege-escalation behavior chains: a medium- or low-integrity process followed by a high-integrity child with anomalous parentage.
- Monitor Windows Error Reporting and crash dumps for faults in the Brokering File System driver that correlate with the same user session.
- Correlate patch inventory data against the affected Windows 11 24H2, Windows Server 2022 23H2, and Windows Server 2025 builds to identify systems still exposed.
Monitoring Recommendations
- Enable process creation auditing (Event ID 4688) with command-line logging to catch integrity level transitions.
- Ingest endpoint telemetry into a centralized data lake or SIEM to enable cross-host correlation of exploitation attempts.
- Track installation status of the May 2025 Patch Tuesday updates across the fleet and alert on hosts that miss the rollup.
How to Mitigate CVE-2025-29970
Immediate Actions Required
- Apply the May 2025 Microsoft security update that addresses CVE-2025-29970 across all affected Windows 11 24H2, Windows Server 2022 23H2, and Windows Server 2025 systems.
- Prioritize patching multi-user hosts, terminal servers, and jump boxes where low-privilege accounts have interactive access.
- Audit local account inventories and remove unnecessary interactive logon rights to shrink the pool of potential attackers.
Patch Information
Microsoft released the fix through the May 13, 2025 security update cycle. Detailed build numbers and download links are available in the Microsoft Security Update Guide for CVE-2025-29970. No official workaround is documented; patch installation is the supported remediation path.
Workarounds
- Restrict local logon rights and remove standard users from systems that do not require interactive access, reducing the population of authorized attackers.
- Enforce application allowlisting through Windows Defender Application Control or AppLocker to block execution of untrusted binaries used to stage exploitation.
- Deploy endpoint detection tooling capable of identifying suspicious integrity-level elevations and terminating the offending process tree.
# Verify installed update status on Windows via PowerShell
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 20
# Confirm current OS build against patched versions listed in the Microsoft advisory
[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.
