CVE-2026-97557: Linux

High severity, CVSS 7.5. EPSS: 0.7% chance of exploitation in the next 30 days.

In the Linux kernel, the following vulnerability has been resolved: smb: client: avoid leaking refcount in cifs_queue_oplock_break() cifs_queue_oplock_break() unconditionally takes a reference on the target file before queueing cifs_oplock_break(). Only that work item decreases the reference counter again. If another oplock break arrives while that work is still queued, queue_work() will return false and not queue this second work item. As a result, we will never reach the point to drop the file reference again and are leaking this reference. This can be triggered when interacting with a slow-responding server. As a result, later unmount operations for this file system will fail with BUG: Dentry ... still in use (1) [unmount of cifs cifs] VFS: Busy inodes after unmount of cifs (cifs) kernel BUG at fs/super.c:777! Fix this by only incrementing the reference count if the work has been queued successfully. Taking it after queue_work() is safe because all three callers hold tcon->open_file_lock across the call and _cifsFileInfo_put() decrements under that same lock, so a worker that starts the handler in the window cannot drop the reference before it has been taken.

Affected products

• Linux Linux: from 3.16.72, before 3.17 (fixed in 3.17); from 4.9.171, before 4.10 (fixed in 4.10); from 4.14.114, before 4.15 (fixed in 4.15); from 4.19.37, before 4.20 (fixed in 4.20); from 5.0.10, before 5.1 (fixed in 5.1); from 5.1, before 6.1.189 (fixed in 6.1.189); …

Published 2026-09-25. Last modified 2026-10-03.