CVE-2026-53996 in NetBSD
Summary
by MITRE • 08/12/2026
NetBSD's hdaudio(4) driver in sys/dev/hdaudio/hdaudio.c contains a missing access control vulnerability that allows unprivileged local attackers to invoke the HDAUDIO_FGRP_SETCONFIG ioctl without elevated permissions by exploiting the absence of an access check on /dev/hdaudioN device nodes. Attackers can repeatedly issue HDAUDIO_FGRP_SETCONFIG from one thread while keeping DMA and IRQs live from a second thread to trigger a use-after-free race condition in hdafg_detach() between stream_stop() and stream_disestablish(), where a latched DMA interrupt dereferences a freed callback pointer, resulting in outcomes ranging from audio-subsystem denial of service and kernel panic to potential local kernel privilege escalation.
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Analysis
by VulDB Data Team • 08/12/2026
The vulnerability resides within NetBSD's hdaudio driver implementation where insufficient access controls permit unauthorized local users to manipulate hardware configuration through the HDAUDIO_FGRP_SETCONFIG ioctl command. This flaw exists due to the absence of proper permission checks on /dev/hdaudioN device nodes, allowing any unprivileged user to invoke privileged operations directly through the audio subsystem interface. The vulnerability manifests as a race condition during device teardown when multiple threads attempt concurrent operations on the same hardware resources.
The technical exploitation involves a sophisticated timing attack where one thread continuously issues HDAUDIO_FGRP_SETCONFIG commands while maintaining active DMA and interrupt operations through a second thread. This creates a precise temporal window during which hdafg_detach() function executes stream_stop() followed by stream_disestablish() operations. The race condition occurs because the kernel's stream management logic fails to properly synchronize access to shared callback structures, leading to memory management inconsistencies.
During this critical race window, a latched DMA interrupt event attempts to dereference a callback pointer that has already been freed by the stream_disestablish() function call. This use-after-free scenario represents a classic memory corruption vulnerability with potentially severe consequences for system stability and security. The kernel's inability to properly validate access permissions before executing hardware configuration changes creates an attack surface where local adversaries can manipulate audio subsystem state.
The operational impact extends beyond simple denial of service conditions, as the memory corruption resulting from the use-after-free can lead to unpredictable kernel behavior including system crashes, kernel panics, and in some cases, potential privilege escalation to kernel-level execution. The vulnerability affects systems running NetBSD with hdaudio hardware support, particularly those utilizing Intel High Definition Audio controllers where the driver's configuration interface is exposed to local users.
This vulnerability maps directly to CWE-284 Access Control Issues, specifically addressing insufficient access control mechanisms in device driver interfaces, and aligns with ATT&CK technique T1068 Privilege Escalation through exploitation of kernel vulnerabilities. The flaw demonstrates a fundamental security weakness in the driver's permission model that fails to enforce proper access controls for hardware configuration operations, creating an attack vector that bypasses normal user privilege boundaries.
Mitigation strategies should include implementing proper access control checks within the ioctl handler for HDAUDIO_FGRP_SETCONFIG, ensuring that only appropriately privileged processes can invoke these operations. Additionally, the driver should implement proper synchronization mechanisms to prevent race conditions during stream management operations. The system should enforce mandatory access controls and consider restricting device node permissions to prevent unauthorized access to hardware configuration interfaces. Kernel hardening measures such as stack canaries, pointer validation, and memory protection mechanisms should also be considered to limit potential exploitation impacts.
The vulnerability highlights the critical importance of proper driver security implementation in operating system kernels, where insufficient access control mechanisms can create persistent attack vectors that remain exploitable across multiple system configurations. Regular security audits of device drivers and kernel interfaces should include comprehensive access control testing to prevent similar issues from emerging in other hardware subsystems. System administrators should ensure that audio hardware drivers are properly configured with appropriate access controls and that unnecessary access permissions are restricted to minimize potential exploitation surfaces.
Security researchers and system maintainers must recognize that driver-level vulnerabilities often represent the most critical attack vectors due to their ability to directly interact with hardware resources and potentially escalate privileges within the kernel space. The combination of insufficient access controls, race condition exploitation, and memory corruption in this vulnerability demonstrates how seemingly minor implementation oversights can create significant security risks requiring immediate attention through both code-level fixes and system-wide security policy enforcement.