CVE-2025-49727: Windows 10 1507 Privilege Escalation Flaw

CVE-2025-49727 Overview

CVE-2025-49727 is a heap-based buffer overflow [CWE-122] in the Windows Win32K graphics subsystem (Win32K - GRFX). The vulnerability allows an authenticated local attacker to corrupt kernel heap memory and elevate privileges on affected systems. Microsoft published the advisory on July 8, 2025, covering supported Windows client and server releases from Windows 10 1507 through Windows 11 24H2 and Windows Server 2008 through Windows Server 2025. Successful exploitation yields SYSTEM-level code execution from a low-privileged user context.

Critical Impact
An authorized local attacker who wins a race in the Win32K graphics component can trigger a heap-based buffer overflow and elevate privileges to SYSTEM, gaining full control of the host.

Affected Products

Microsoft Windows 10 (1507, 1607, 1809, 21H2, 22H2)
Microsoft Windows 11 (22H2, 23H2, 24H2)
Microsoft Windows Server (2008 SP2, 2008 R2, 2012, 2012 R2, 2016, 2019, 2022, 2022 23H2, 2025)

Discovery Timeline

2025-07-08 - CVE-2025-49727 published to NVD and Microsoft releases security update
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-49727

Vulnerability Analysis

The flaw resides in the Windows kernel-mode Win32K graphics component (Win32K - GRFX), which handles graphics device interface (GDI) objects on behalf of user-mode processes. A heap-based buffer overflow occurs when the driver writes past the bounds of a kernel heap allocation while processing attacker-controlled graphics data. Because Win32K runs in kernel mode, corruption of adjacent pool memory can be leveraged to overwrite kernel structures and hijack execution.

Exploitation requires local access with valid credentials and elevated attack complexity, which suggests a race condition or a specific memory-layout precondition must be met. Once achieved, the attacker gains high impact to confidentiality, integrity, and availability by escalating to SYSTEM.

Root Cause

The root cause is improper validation of size or length parameters when allocating or writing to a heap buffer inside the Win32K graphics kernel driver. The condition falls under [CWE-122] Heap-based Buffer Overflow. An attacker crafts input to a graphics-related syscall that causes the driver to write more data than the destination pool allocation can hold, corrupting adjacent kernel objects.

Attack Vector

A local, authenticated attacker executes a specially crafted user-mode process that issues graphics-related system calls into the Win32K subsystem. By manipulating pool allocations and timing the overflow-triggering call, the attacker overwrites kernel objects such as pipe attributes or GDI headers to gain arbitrary kernel read/write. This primitive is then used to steal a SYSTEM token or patch process privilege structures. The vulnerability cannot be exploited remotely and requires no user interaction beyond the attacker's own session.

No public proof-of-concept exploit is available for CVE-2025-49727 at this time, and it is not listed in the CISA Known Exploited Vulnerabilities catalog.

Detection Methods for CVE-2025-49727

Indicators of Compromise

Unexpected SYSTEM-privileged child processes spawned from standard user sessions or interactive desktops.
Kernel bugchecks (BSODs) referencing win32kfull.sys, win32kbase.sys, or win32k.sys on hosts running unpatched builds.
New or modified services, scheduled tasks, or local accounts created immediately after a non-administrative logon.

Detection Strategies

Hunt for token-manipulation patterns where a low-integrity process suddenly executes with SYSTEM integrity.
Correlate process-creation telemetry with unusual GDI or graphics API call sequences from non-graphical binaries.
Monitor Windows Error Reporting and crash dumps for repeated Win32K faults, which can indicate exploit development attempts.

Monitoring Recommendations

Ingest Sysmon Event IDs 1 (process create) and 10 (process access) into a SIEM and alert on cross-integrity-level access to lsass.exe or winlogon.exe.
Enable Microsoft Defender Attack Surface Reduction rules that block credential theft and abuse of exploited vulnerable drivers.
Track patch-compliance state for KB updates covering CVE-2025-49727 across all Windows client and server assets.

How to Mitigate CVE-2025-49727

Immediate Actions Required

Apply the Microsoft July 2025 security updates that address CVE-2025-49727 to all affected Windows versions.
Prioritize patching multi-user systems such as terminal servers, VDI hosts, and shared workstations where local users are untrusted.
Audit local account membership and remove unnecessary interactive logon rights on servers.

Patch Information

Microsoft published a fix in the July 8, 2025 security update cycle. Refer to the Microsoft CVE-2025-49727 Advisory for the KB article corresponding to each affected build and install the cumulative update through Windows Update, WSUS, or Microsoft Update Catalog.

Workarounds

No official workaround exists; applying the vendor patch is the only supported remediation.
Restrict local logon and remote desktop access to trusted administrators until patching is complete.
Enable Hypervisor-protected Code Integrity (HVCI) and Credential Guard to raise the cost of kernel exploitation.

bash

# Verify installed updates and patch level on Windows
wmic qfe list brief /format:table
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 20

# Force Windows Update scan and install
UsoClient StartScan
UsoClient StartInstall