CVE-2026-74497 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
ALSA: usb-audio: Clamp frame size in implicit-feedback mode
snd_usb_handle_sync_urb() scales received sync packet sizes by the sender's stride and stores the result directly in out_packet->packet_size[i]. If a
connected USB device sends an oversized sync packet, this frame count can exceed ep->maxframesize.
The un-clamped frame count then propagates to the playback endpoint queue, potentially driving packet transfers beyond the endpoint's hardware frame limits.
Cap the calculated frame count against ep->maxframesize in snd_usb_handle_sync_urb() to prevent oversized packets from entering the playback queue.
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Analysis
by VulDB Data Team • 08/15/2026
This vulnerability resides within the Linux kernel's advanced linux sound architecture subsystem specifically affecting usb-audio device drivers. The issue manifests in the snd_usb_handle_sync_urb() function which processes synchronization packets for USB audio devices operating in implicit-feedback mode. When a connected USB audio device transmits oversized synchronization packets, the system fails to properly validate the frame size calculations against hardware limitations, creating a potential pathway for buffer overflow conditions. The flaw stems from direct assignment of calculated packet sizes without proper bounds checking against endpoint maximum frame size limits, representing a classic case of insufficient input validation and output sanitization.
The technical execution of this vulnerability occurs through the improper handling of USB synchronization data where the system scales received sync packet sizes by the sender's stride value and immediately stores the result in the output packet structure. This direct assignment bypasses any bounds checking mechanisms that should validate whether the calculated frame count remains within acceptable hardware limits defined by ep->maxframesize. When oversized packets are processed, they can cause the playback endpoint queue to attempt transfers exceeding the physical hardware capabilities of the USB audio endpoint, potentially leading to system instability or denial of service conditions.
The operational impact of this vulnerability extends beyond simple performance degradation to encompass potential system stability risks and resource exhaustion scenarios. Attackers could leverage this condition by connecting malicious USB audio devices that send oversized synchronization packets, causing the kernel's USB audio subsystem to queue invalid packet transfers that exceed hardware specifications. Such exploitation could result in system hangs, kernel panics, or forced device disconnections during audio playback operations, particularly affecting systems running real-time audio applications where endpoint boundaries are critical for maintaining proper data flow.
Mitigation strategies should focus on implementing proper bounds checking within the snd_usb_handle_sync_urb() function to clamp calculated frame sizes against the maximum frame size limits defined by ep->maxframesize. This approach aligns with established security practices for preventing buffer overflows and maintaining system integrity in kernel space operations. The fix requires modifying the packet size assignment logic to include validation checks that ensure calculated values never exceed hardware-defined limits, thereby preventing oversized packets from entering the playback queue. This remediation directly addresses the root cause identified in CWE-129 Input Validation and Output Encoding, specifically targeting the improper handling of boundary conditions in kernel-level USB audio processing operations.
The vulnerability demonstrates characteristics consistent with ATT&CK technique T1068, which involves exploitation of system vulnerabilities to gain elevated privileges or cause system instability. In this context, the flaw could potentially be exploited by attackers with physical access to systems running affected kernels, particularly targeting embedded systems or devices where USB audio functionality is critical for operation. Implementation of proper input validation and bounds checking mechanisms provides defense in depth against such attacks while maintaining compatibility with legitimate USB audio device operations and preserving the intended functionality of the implicit-feedback mode.
This specific vulnerability represents a narrow but critical flaw in USB audio processing that affects systems using the Linux kernel's ALSA subsystem, particularly those supporting USB audio devices in implicit-feedback configurations. The fix ensures proper clamping of frame sizes during synchronization packet handling, preventing memory corruption scenarios that could lead to system crashes or unauthorized access to kernel memory regions. The resolution maintains backward compatibility while strengthening the robustness of USB audio endpoint management through improved validation of hardware boundary conditions.