CVE-2026-89868 Overview
CVE-2026-89868 affects the Linux kernel's chips-media wave5 video processing unit (VPU) driver. The flaw resides in the stop_streaming code path of the media subsystem. Under certain conditions, the function enters an infinite loop while waiting for queues to drain. The upstream fix introduces a bounded poll of the queue status, sleeping briefly between checks and exiting once VPU_DEC_STOP_TIMEOUT elapses. The issue impacts local kernel stability and can render the video decode subsystem unresponsive on affected hardware platforms that use the Chips&Media Wave5 VPU.
Critical Impact
A local trigger of stop_streaming on the wave5 VPU driver can cause an unbounded kernel loop, leading to denial of service on the affected media pipeline.
Affected Products
- Linux kernel media subsystem — drivers/media/platform/chips-media/wave5
- Linux stable branches referenced in commits 2ae7faed and c104f37b
- Systems using Chips&Media Wave5 VPU hardware for video decode
Discovery Timeline
- 2026-09-16 - CVE-2026-89868 published to NVD
- 2026-09-16 - Last updated in NVD database
Technical Details for CVE-2026-89868
Vulnerability Analysis
The vulnerability lives in the stop_streaming handler of the Chips&Media Wave5 VPU driver, part of the Linux V4L2 media framework. When userspace stops a streaming session, the driver waits for pending queues to drain before releasing buffers and returning control. The original implementation lacked a bounded wait, so if the hardware or firmware failed to signal queue completion, the kernel thread spun indefinitely. This behavior manifests as a hung task, unresponsive video pipeline, or an unkillable process holding the VPU device open.
The patched code replaces the unbounded wait with a bounded poll. The driver repeatedly checks queue status, sleeps briefly between checks, and aborts once VPU_DEC_STOP_TIMEOUT elapses. This turns an indefinite hang into a recoverable error path.
Root Cause
The root cause is missing timeout enforcement in a kernel wait loop, a classic Denial of Service pattern tied to Infinite Loop conditions. The driver trusted the hardware to always report queue drain completion. Any firmware fault, hardware stall, or ordering issue that prevents the drain signal leaves the kernel thread looping without progress.
Attack Vector
Exploitation requires local access to a system exposing the Wave5 VPU device node, typically /dev/videoX. A local user with permission to open the device and issue V4L2 streaming ioctls can trigger the affected stop_streaming path. Successful triggering causes a hung task in kernel space and can require a reboot to fully recover the media subsystem. No remote attack surface has been documented for this issue.
For technical details, see the upstream commits: Kernel Git Commit 2ae7faed and Kernel Git Commit c104f37b.
Detection Methods for CVE-2026-89868
Indicators of Compromise
- Kernel log entries reporting hung_task warnings referencing wave5 driver threads or stop_streaming call paths.
- Processes stuck in uninterruptible sleep (D state) while holding open a Wave5 VPU /dev/videoX node.
- Video decode pipelines that fail to release buffers or respond to VIDIOC_STREAMOFF requests.
Detection Strategies
- Monitor dmesg and /var/log/kern.log for INFO: task ... blocked for more than N seconds messages tied to the wave5 module.
- Audit kernel version and module metadata to identify hosts running vulnerable wave5 driver builds without the timeout patch applied.
- Track userspace processes making repeated VIDIOC_STREAMOFF ioctl calls against wave5 device nodes.
Monitoring Recommendations
- Enable hung_task detection with kernel.hung_task_timeout_secs set to a value appropriate for the workload.
- Forward kernel logs to a centralized SIEM or data lake for correlation of hung-task events across fleet hosts.
- Alert on sustained D-state processes bound to media device files on systems running affected kernel versions.
How to Mitigate CVE-2026-89868
Immediate Actions Required
- Apply the upstream Linux stable kernel patches referenced in commits 2ae7faed and c104f37b and rebuild affected kernels.
- Inventory systems that load the wave5 module and prioritize patching hosts with untrusted local users.
- Restrict access to Wave5 VPU device nodes to trusted users and service accounts only.
Patch Information
The fix adds a bounded poll of the queue status inside stop_streaming. The driver now sleeps briefly between checks and returns once VPU_DEC_STOP_TIMEOUT elapses, converting the previous infinite wait into a recoverable timeout. Consume the fix through the Linux stable tree updates linked in Kernel Git Commit 2ae7faed and Kernel Git Commit c104f37b, or upgrade to a distribution kernel that has backported these commits.
Workarounds
- Blacklist the wave5 kernel module on hosts that do not require Chips&Media VPU hardware decode.
- Tighten permissions on /dev/video* nodes exposed by the wave5 driver using udev rules or group ownership.
- Restart affected services or reboot hosts that exhibit hung stop_streaming threads until a patched kernel is deployed.
# Prevent the vulnerable module from loading until a patched kernel is deployed
echo "blacklist wave5" | sudo tee /etc/modprobe.d/blacklist-wave5.conf
sudo depmod -a
sudo update-initramfs -u
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
