CVE-2026-69731 Overview
CVE-2026-69731 is a heap-based buffer overflow vulnerability in the Windows Human Interface Device (HID) class driver. An authorized local attacker can exploit the flaw to elevate privileges on affected systems. The weakness maps to [CWE-122], heap-based buffer overflow, and stems from improper bounds handling during HID request processing in kernel-mode driver code. Successful exploitation grants attackers higher privileges, providing full control over confidentiality, integrity, and availability of the target host. Microsoft published the advisory through its Security Update Guide.
Critical Impact
A local authorized attacker who exploits the HID class driver overflow can execute code in kernel context and gain SYSTEM-level privileges.
Affected Products
- Microsoft Windows (HID class driver component)
- Refer to the Microsoft CVE-2026-69731 Update Guide for the complete list of affected builds
- Specific Windows versions and KB identifiers are enumerated in the vendor advisory
Discovery Timeline
- 2026-09-08 - CVE-2026-69731 published to NVD
- 2026-09-09 - Last updated in NVD database
Technical Details for CVE-2026-69731
Vulnerability Analysis
The vulnerability resides in the Windows HID class driver, a kernel-mode component that manages input from human interface devices such as keyboards, mice, and USB peripherals. The driver processes HID reports and descriptors passed from lower-level transport drivers. A heap-based buffer overflow [CWE-122] occurs when the driver writes attacker-influenced data beyond the bounds of a pool allocation.
Because the code runs in kernel context, an overflow into an adjacent pool chunk can corrupt kernel objects. Attackers can shape the pool layout to place a controllable object next to the vulnerable allocation. Overwriting function pointers or object headers then redirects execution into attacker-controlled memory.
Exploitation requires local access and a low-privileged account, but no user interaction. The scope remains unchanged, and successful exploitation results in high impact to confidentiality, integrity, and availability.
Root Cause
The root cause is missing or incorrect validation of a length or size field used when copying HID data into a heap-allocated kernel buffer. The driver trusts a size derived from device-supplied or user-supplied input without enforcing an upper bound against the destination allocation.
Attack Vector
A local attacker with the ability to interact with the HID subsystem, for example by issuing IOCTLs to the driver or by attaching a crafted virtual HID device, can trigger the overflow. Precise technical mechanics are not published in the public advisory. Consult the Microsoft CVE-2026-69731 Update Guide for vendor-provided details.
Detection Methods for CVE-2026-69731
Indicators of Compromise
- Unexpected kernel bugchecks or BAD_POOL_HEADER and KERNEL_MODE_HEAP_CORRUPTION stop errors referencing hidclass.sys
- Creation of new SYSTEM-level processes spawned from low-privileged user sessions shortly after HID device enumeration events
- Installation or loading of unsigned or unusual virtual HID drivers on endpoints without hardware changes
Detection Strategies
- Monitor kernel crash telemetry for faults in hidclass.sys correlated with the loading of user-controlled device drivers
- Alert on privilege escalation patterns where a non-administrative user token is replaced with a SYSTEM token in an existing process
- Baseline HID device enumeration on servers and workstations, and flag anomalous device attach events from user-mode processes
Monitoring Recommendations
- Enable Windows Kernel-PnP and Kernel-Power event channels to capture driver load and device attach activity
- Forward endpoint driver load events and process token changes to a centralized SIEM for correlation
- Track patch compliance for the Microsoft security update addressing CVE-2026-69731 across all Windows endpoints
How to Mitigate CVE-2026-69731
Immediate Actions Required
- Apply the Microsoft security update referenced in the Microsoft CVE-2026-69731 Update Guide to all affected Windows systems
- Prioritize patching on multi-user hosts, jump servers, and workstations where low-privileged users can execute arbitrary code
- Audit local accounts and remove unnecessary interactive logon rights to reduce the attacker population
Patch Information
Microsoft has issued a security update through its standard servicing channels. Administrators should consult the vendor advisory to identify the specific KB article and cumulative update matching each Windows build in their environment. Deploy the update through Windows Update, WSUS, Microsoft Intune, or Configuration Manager.
Workarounds
- No official vendor workaround is listed; applying the security update is the recommended remediation
- Restrict physical and remote access to endpoints to limit local exploitation opportunities
- Use application control policies such as Windows Defender Application Control to block unauthorized user-mode tooling that could stage the exploit
# Verify installation status of the Microsoft security update on Windows
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Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
