CVE-2026-97996

Overview

CVE-2026-97996 is a Linux kernel use-after-free in virtio device unregistration. It occurs when certain virtio transports free the embedded virtio_device before unregister_virtio_device() reads debugfs state. It matters because local device unbind operations can trigger memory corruption on affected kernels.

Description

In the Linux kernel, the following vulnerability has been resolved: virtio: fix use-after-free in unregister_virtio_device() device_unregister() is device_del() plus put_device(). When the caller holds no extra reference, that drops the last one and runs the release callback, which for several transports frees the memory the embedded struct virtio_device sits in. unregister_virtio_device() then calls virtio_debug_device_exit(), which reads dev->debugfs_dir out of the freed object. Affected transports are the ones whose release callback frees and whose remove path takes no reference: virtio_mmio, virtio_vdpa, virtio_uml, mlxbf-tmfifo and virtio_ccw. virtio_pci is unaffected because virtio_pci_remove() brackets the call with get_device() and put_device(). Remove the debugfs entries before the device can go away. They are only accessed through the protected debugfs interface, so debugfs_remove_recursive() waits for in-progress file operations before returning. Tearing them down while the device is still alive is therefore safe. Reproduced on User-Mode Linux with CONFIG_KASAN and CONFIG_VIRTIO_DEBUG by unbinding a virtio-uml device: BUG: KASAN: slab-use-after-free in virtio_debug_device_exit+0x36/0x4d Read of size 8 at addr 00000000616e0b10 by task init/1 __asan_report_load8_noabort virtio_debug_device_exit+0x36/0x4d unregister_virtio_device+0x48/0x75 virtio_uml_remove platform_remove device_release_driver_internal unbind_store Freed by task 1: kfree virtio_uml_release_dev device_release kobject_put put_device device_unregister With this applied, the report is gone and unbind is clean.

Impact

Confidentiality and integrity may be affected if an attacker can trigger the use-after-free through local virtio device removal. Availability may be impacted through kernel memory corruption or denial of service. The primary risk is to systems running affected virtio transports where local users or processes can unbind virtio devices. Exposure is generally limited to environments with local access and affected kernel configurations.

Remediation

Apply the vendor kernel update or backport that removes virtio debugfs entries before the device can be released. Update affected Linux kernel packages to a fixed release. Restrict local access to virtio device management interfaces, including sysfs unbind paths, to trusted administrators. Disable CONFIG_VIRTIO_DEBUG where not required for support or diagnostics. Monitor for unexpected virtio device unbind events and kernel memory-safety warnings.

Risk context

The reported CVSS v3 score is 7.8, indicating high severity. No EPSS value is provided, so exploitation likelihood should be assessed from local exposure, affected virtio transports, and kernel configuration. Defenders should prioritize patching where untrusted local users can manage virtio devices or where affected transports are in use.

Affected products

• Linux kernel
• virtio_mmio
• virtio_vdpa
• virtio_uml
• mlxbf-tmfifo
• virtio_ccw