Windows Kernel Driver Vulnerability Exposes Systems to Heap-Based Attacks

Security researchers have disclosed a heap-based buffer overflow vulnerability in Microsoft Windows’ Kernel Streaming WOW Thunk Service Driver, designated as CVE-2025-53149.

The flaw, discovered in the ksthunk.sys driver component was responsibly disclosed to Microsoft and subsequently patched, highlighting ongoing security concerns within Windows kernel-level multimedia processing infrastructure.

The vulnerable component, identified by SHA-1 hash 68B5B527550731DD657BF8F1E8FA31E895A7F176, represents a critical weakness in Windows’ multimedia streaming architecture that could potentially allow attackers to execute arbitrary code with elevated privileges through carefully crafted IOCTL (Input/Output Control) requests.

Technical Analysis and Attack Vector

The vulnerability originates within the CKSAutomationThunk::HandleArrayProperty() function, which processes property requests for multimedia devices supporting the KSPROPSETID_VPConfig and KSPROPSETID_VPVBIConfig property sets.

The security flaw manifests during property retrieval operations when the function fails to properly validate output buffer lengths against data returned from KsSynchronousIoControlDevice() calls.

According to the technical analysis, the vulnerable code path emerges when processing KSPROPERTY_VPCONFIG_DDRAWSURFACEHANDLE property requests.

The function performs two sequential calls to KsSynchronousIoControlDevice(): the first determines the required buffer size, while the second retrieves the actual array data.

However, the critical security oversight occurs during the buffer copying phase, where the OutputBufferLength parameter undergoes insufficient validation—being checked only against zero rather than against the actual BytesReturned value.

This validation gap creates a classic heap-based buffer overflow condition within the kernel’s non-paged memory pool.

When the returned data exceeds the allocated output buffer capacity, subsequent memory copying operations can overwrite adjacent heap structures, potentially leading to system compromise through arbitrary code execution or privilege escalation attacks.

The exploitation mechanism requires attackers to craft malicious IOCTL requests targeting multimedia devices that implement the vulnerable property handlers.

Specifically, exploitation involves opening device handles and issuing IOCTL_KS_PROPERTY requests with carefully constructed KSPROPERTY structures containing KSPROPERTY_TYPE_GET and KSPROPERTY_TYPE_COPYPAYLOAD flags.

However, successful exploitation presents practical challenges, as it requires target systems to possess multimedia hardware devices implementing the affected property sets.

During security testing, researchers encountered difficulties locating compatible devices on standard test systems, suggesting that exploitation may be limited to specific hardware configurations or specialized multimedia environments.

Microsoft’s remediation approach involved implementing additional buffer length validation within the HandleArrayProperty() function.

The patched version now includes explicit checks comparing OutputBufferLength against the actual data size returned from device queries.

When insufficient buffer space is detected, the code safely redirects execution to RtlLogUnexpectedCodepath(), preventing potential overflow conditions while maintaining system stability.

The disclosure timeline reveals a coordinated effort spanning several months, from initial discovery in April 2025 through final patch deployment in August 2025.

This timeline demonstrates both the complexity of kernel-level vulnerability assessment and Microsoft’s commitment to addressing critical security issues within its multimedia subsystem infrastructure.

This vulnerability underscores the ongoing security challenges inherent in complex kernel driver ecosystems, particularly those handling real-time multimedia streaming operations.

Organizations utilizing Windows systems with specialized multimedia hardware should prioritize applying Microsoft’s August 2025 security updates to mitigate potential exploitation risks associated with CVE-2025-53149.

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