Vulnerability record · CVE-2025-40249 · published 4 December 2025
CVE-2025-40249: In the Linux kernel, the following vulnerability has been resolved: gpio: cdev: make sure the cdev fd is stil…
In the Linux kernel, the following vulnerability has been resolved: gpio: cdev: make sure the cdev fd is still active before emitting events With the final call to fput() on a file descriptor, the release action may be deferred and scheduled on a work queue. The reference count of that descriptor is still zero and it must not be used. It's possible that a GPIO change, we want to notify the user-space about, happens AFTER the reference count on the file descriptor associated with the character device went down to zero but BEFORE the .release() callback was called from the workqueue and so BEFORE we unregistered from the notifier. Using the regular get_file() routine in this situation triggers the following warning: struct file::f_count incremented from zero; use-after-free condition present! So use the get_file_active() variant that will return NULL on file descriptors that have been or are being released.
Description
In the Linux kernel, the following vulnerability has been resolved: gpio: cdev: make sure the cdev fd is still active before emitting events With the final call to fput() on a file descriptor, the release action may be deferred and scheduled on a work queue. The reference count of that descriptor is still zero and it must not be used. It's possible that a GPIO change, we want to notify the user-space about, happens AFTER the reference count on the file descriptor associated with the character device went down to zero but BEFORE the .release() callback was called from the workqueue and so BEFORE we unregistered from the notifier. Using the regular get_file() routine in this situation triggers the following warning: struct file::f_count incremented from zero; use-after-free condition present! So use the get_file_active() variant that will return NULL on file descriptors that have been or are being released.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
References
Track CVE-2025-40249 inside VULONE
Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.
Source: NIST National Vulnerability Database (record CVE-2025-40249), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.
