CVE-2026-89868 in Linux
Summary
by MITRE • 09/16/2026
In the Linux kernel, the following vulnerability has been resolved:
media: chips-media: wave5: Add timeout while stop_streaming
When stop_streaming is called, an infinite loop may occur in some cases. Add a bounded poll of the queue status: loop until the queues drain, sleeping briefly between polls, and bail out once VPU_DEC_STOP_TIMEOUT elapses.
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Analysis
by VulDB Data Team • 09/16/2026
The Linux kernel media subsystem contains a driver for chips-media wave5 video processing units that previously suffered from a critical reliability flaw within its stream management logic. Specifically, when the stop_streaming function was invoked to halt data acquisition or playback operations, the underlying implementation lacked an upper bound on the waiting period required for hardware queues to drain completely. This architectural oversight meant that if the Video Processing Unit failed to acknowledge the stop command in a timely manner due to internal errors, driver state inconsistencies, or external system hangs, the kernel thread executing the cleanup routine would enter an infinite loop. Such behavior effectively results in a denial of service condition where the calling process becomes permanently blocked, consuming CPU resources and preventing other operations from proceeding until a manual intervention such as a hard reset is performed by the system administrator.
From a technical perspective, this vulnerability represents a classic failure to implement proper timeout mechanisms for hardware synchronization primitives. The original code relied on an unbounded wait condition that assumed ideal hardware behavior where queues would always drain within a predictable timeframe. In real-world deployments involving embedded systems or high-load environments, hardware responses can be delayed indefinitely due to resource contention, firmware bugs, or peripheral faults. By failing to account for these edge cases, the driver violated fundamental principles of robust system design which dictate that all blocking operations must have defined expiration criteria to prevent indefinite suspension of execution threads. This flaw aligns with CWE-835, known as a loop with unreachable exit condition, where the control flow structure lacks a guaranteed termination path under certain error states or hardware failures.
The operational impact of this vulnerability extends beyond simple process hanging. In multi-threaded applications or systems relying on asynchronous media processing pipelines, an infinite block in stop_streaming can cause cascading failures across dependent services. For instance, if a video recording application cannot release its stream resources due to this hang, it may fail to start new sessions, leading to service degradation for end-users. Furthermore, because the kernel thread is stuck in user-space-triggered context without yielding control appropriately over extended periods, it can contribute to overall system latency and reduced responsiveness. In security terms, while primarily a stability issue, such hangs can be exploited by local attackers with sufficient privileges to trigger media operations repeatedly, thereby exhausting available threads or causing sustained denial of service against critical infrastructure components that depend on stable video processing capabilities.
To mitigate this risk, the vulnerability was addressed by introducing a bounded polling mechanism within the stop_streaming routine. The updated implementation now performs periodic checks on the queue status with brief sleep intervals between polls rather than spinning indefinitely. Crucially, it incorporates a predefined timeout constant, VPU_DEC_STOP_TIMEOUT, which dictates the maximum duration the driver will wait for the hardware to acknowledge the stop command. Once this threshold is exceeded without successful queue draining, the function aborts the operation and returns an error code instead of continuing to block execution. This change ensures that resource cleanup processes remain responsive even when the underlying hardware becomes unresponsive, thereby preserving system stability and allowing higher-level applications to handle errors gracefully rather than crashing or hanging indefinitely.
This fix reinforces adherence to best practices for kernel driver development regarding timeout management and resource lifecycle control. It also aligns with ATT&CK technique T1499, Endpoint Denial of Service, by removing a vector that could be used to disrupt local system availability through maliciously timed media stream termination requests. By enforcing strict time limits on hardware synchronization points, the patch significantly improves the resilience of the Linux kernel against both accidental faults and intentional abuse scenarios targeting media subsystems. System administrators should ensure their kernels are updated with this patch applied to maintain operational continuity in environments where video processing is a critical component of system functionality.