CVE-2025-49667: Windows 10 1507 Privilege Escalation Flaw

CVE-2025-49667 Overview

CVE-2025-49667 is a double free vulnerability in the Windows Win32K Input Compatibility (ICOMP) component. The flaw allows an authenticated local attacker to elevate privileges on affected Windows 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 R2 through Windows Server 2025. The weakness is categorized as [CWE-415] Double Free, a memory corruption class frequently exploited for kernel-mode privilege escalation.

Critical Impact

Successful exploitation grants SYSTEM-level privileges from a low-privileged user context, enabling full host compromise.

Affected Products

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

Discovery Timeline

• 2025-07-08 - CVE-2025-49667 published to NVD with Microsoft advisory
• 2025-07-15 - Last updated in NVD database

Technical Details for CVE-2025-49667

Vulnerability Analysis

The vulnerability resides in the Win32K kernel-mode subsystem, specifically the Input Compatibility (ICOMP) component. Win32K handles window management, graphics device interface (GDI), and user input across all Windows versions. A double free condition occurs when the same memory region is released twice through ExFreePool or related kernel allocator paths.

Double free conditions corrupt kernel pool metadata and freelist structures. An attacker controlling adjacent allocations can manipulate this corruption to gain arbitrary kernel read/write primitives. From there, attackers typically overwrite the _EPROCESS token field to inherit SYSTEM privileges.

The attack requires local authenticated access with low privileges. No user interaction is needed beyond running the exploit binary. The EPSS score of 0.774% reflects moderate exploit prediction likelihood for this class of kernel flaw.

Root Cause

The root cause is improper object lifetime management within the ICOMP code path. When a kernel object reference count reaches zero through two separate code paths, the same allocation is freed twice. The second free operation corrupts the kernel pool allocator state, creating a controllable memory corruption primitive.

Attack Vector

Exploitation requires local code execution as a standard user. The attacker invokes the vulnerable Win32K syscall sequence to trigger the double free. The vulnerability manifests through specific input compatibility processing logic. Refer to the Microsoft Security Update CVE-2025-49667 advisory for affected build numbers and patch identifiers.

Detection Methods for CVE-2025-49667

Indicators of Compromise

• Unexpected win32k.sys or win32kbase.sys kernel crashes recorded as BAD_POOL_HEADER (0x19) or KERNEL_MODE_HEAP_CORRUPTION (0x13A) bugchecks
• Low-privileged processes spawning child processes running as NT AUTHORITY\SYSTEM without legitimate elevation paths
• Anomalous token duplication or process token swap events involving non-administrative parent processes

Detection Strategies

• Monitor for processes that abruptly change integrity level from Medium to System without invoking documented elevation mechanisms
• Hunt for unsigned or unusual binaries issuing rapid sequences of GDI or USER syscalls associated with ICOMP code paths
• Correlate kernel crash telemetry with subsequent privilege escalation activity on the same host

Monitoring Recommendations

• Enable Windows Defender Exploit Guard and kernel pool integrity checks where supported
• Forward Sysmon Event ID 1 (process creation) and Event ID 10 (process access) to a centralized SIEM for behavioral analysis
• Track Windows Error Reporting submissions related to Win32K faults across the fleet to identify exploitation attempts

How to Mitigate CVE-2025-49667

Immediate Actions Required

• Apply the Microsoft July 2025 security update to all affected Windows client and server systems
• Prioritize patching on multi-user systems, terminal servers, and Virtual Desktop Infrastructure (VDI) hosts where local users are present
• Audit local account inventory and remove unnecessary interactive logon rights for non-administrative accounts

Patch Information

Microsoft released fixes through the July 2025 Patch Tuesday cycle. Administrators should consult the Microsoft Security Update CVE-2025-49667 advisory for KB article numbers and specific build versions. Patches are available via Windows Update, WSUS, and the Microsoft Update Catalog for all supported Windows 10, Windows 11, and Windows Server releases.

Workarounds

• No official workaround exists from Microsoft; patching is the only supported mitigation
• Restrict local logon rights through Group Policy User Rights Assignment to limit attacker access
• Deploy application allowlisting via Windows Defender Application Control (WDAC) or AppLocker to block unauthorized binaries from executing

# Verify patch installation status via PowerShell
Get-HotFix | Where-Object { $_.InstalledOn -ge (Get-Date '2025-07-08') } | Sort-Object InstalledOn -Descending

# Query Windows build to confirm patched version
[System.Environment]::OSVersion.Version