CVE-2026-97557: Linux Vulnerability (CVSS 7.5)

Description

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.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= b98749cac4a695f084a5ff076f4510b23e353ecd, < af0193bbf1ac8c0f67f972998b0cc629d6116cf6; >= b98749cac4a695f084a5ff076f4510b23e353ecd, < 2ed2c29dd9593637cfa25ac1eb23241b20202778; >= b98749cac4a695f084a5ff076f4510b23e353ecd, < dfe7b750c7e069873a8a57a11c816831a235618a; >= b98749cac4a695f084a5ff076f4510b23e353ecd, < 9f2e63f1b2d5fc5b5423424902c091123e220e7e; 2429fcf06d3cb962693868ab0a927c9038f12a2d; 1ee4f2d7cdcd4508cc3cbe3b2622d7177b89da12; 53fc31a4853e30d6e8f142b824f724da27ff3e40; 8092ecc306d81186a64cda42411121f4d35aaff4; ebac4d0adf68f8962bd82fcf483936edd6ec095b; >= 3.16.72, < 3.17; >= 4.9.171, < 4.10; >= 4.14.114, < 4.15; >= 4.19.37, < 4.20; >= 5.0.10, < 5.1
Linux	Linux	5.1

References

Timeline

Published: Sep 25, 2026
Last Modified: Sep 25, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-97557?

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.

How severe is CVE-2026-97557?

CVE-2026-97557 has a CVSS score of 7.5/10 (HIGH severity).

How do I fix CVE-2026-97557?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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