CVE-2025-40223: most: usb: Fix use-after-free in hdm_disconnect
In the Linux kernel, the following vulnerability has been resolved:
most: usb: Fix use-after-free in hdmdisconnect
hdmdisconnect() calls mostderegisterinterface(), which eventually unregisters the MOST interface device with deviceunregister(iface->dev). If that drops the last reference, the device core may call releasemdev() immediately while hdmdisconnect() is still executing.
The old code also freed several mdev-owned allocations in hdmdisconnect() and then performed additional putdevice() calls. Depending on refcount order, this could lead to use-after-free or double-free when releasemdev() ran (or when unregister paths also performed puts).
Fix by moving the frees of mdev-owned allocations into releasemdev(), so they happen exactly once when the device is truly released, and by dropping the extra putdevice() calls in hdmdisconnect() that are redundant after deviceunregister() and mostderegisterinterface().
This addresses the KASAN slab-use-after-free reported by syzbot in hdmdisconnect(). See report and stack traces in the bug link below.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 6.17.0-14.14.1 - Compensating control
In the Linux kernel most USB hdm_disconnect() implementation, move all frees of mdev-owned allocations into release_mdev() so they occur exactly once when the device is truly released, and remove the redundant extra put_device() calls after device_unregister() and most_deregister_interface().
Event History
Frequently Asked Questions
What is the severity of CVE-2025-40223?
CVE-2025-40223 is classified as a medium severity vulnerability affecting the Linux kernel.
How does CVE-2025-40223 impact the system?
CVE-2025-40223 can lead to a use-after-free condition in the Linux kernel, potentially causing system instability or crashes.
How do I fix CVE-2025-40223?
To fix CVE-2025-40223, update your Linux kernel to the latest stable version that includes the security patch for this vulnerability.
Which versions of the Linux kernel are affected by CVE-2025-40223?
CVE-2025-40223 affects multiple versions of the Linux kernel prior to the application of the relevant security patches.
Is CVE-2025-40223 a remote or local vulnerability?
CVE-2025-40223 is considered a local vulnerability as it requires local access to exploit the use-after-free condition.