CVE-2025-39997: 
Linux Kernel vulnerability analysis and mitigation

CVE-2025-39997 is a vulnerability discovered in the Linux kernel's ALSA USB audio subsystem, specifically affecting the sndusbmidifree functionality. The vulnerability was disclosed on October 15, 2025, and involves a race condition that can lead to Use-After-Free (UAF) issues (NVD).

The vulnerability stems from a race condition in the error timer handling and URB (USB Request Block) cleanup process. While a previous patch (commit 0718a78f6a9f) attempted to address a UAF issue related to the error timer, the fix was incomplete as the error timer kill operation occurs after the endpoint deletion. Additionally, the missing kill-cleanup for URB can result in accessing freed memory in interrupt context, potentially causing UAF conditions (NVD).

The vulnerability can lead to Use-After-Free conditions in the Linux kernel's USB audio subsystem, potentially allowing access to freed memory in interrupt context. This could result in system instability or potential security implications in the ALSA USB audio functionality (NVD).

The fix involves ensuring that both the error timer and URB are properly killed before freeing the heap memory. This prevents the race condition and subsequent UAF issues from occurring (NVD).