CVE-2026-97558 smb: client: fix cifsFileInfo reference leak in deferred close
A reference leak in the Linux kernel SMB client allows local attackers to exhaust memory and cause denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-97558?
CVE-2026-97558 is a memory corruption vulnerability in Linux, published on 25 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix cifsFileInfo reference leak in deferred close
When cifs_close() defers a close, it hands the cifsFileInfo reference of the closing struct file to the queued work. Each execution of smb2_deferred_work_close() drops one such reference.
deferred_close_scheduled can be false while the work is pending: the workqueue clears PENDING when the callback starts to run, before the callback clears the flag under deferred_lock. A close in that interval requeues the running work, and the callback then clears the flag, leaving the requeued work pending with the flag down. A later cifs_open() can reuse the handle and its cifs_close() reaches the same branch: queue_delayed_work() fails because the work is still pending, but cifs_close() returns without dropping the closing file's reference. The cifsFileInfo count stays pinned and its tlink, dentry and server handle are leaked.
Check the return value and hand off the reference only when work was actually queued. Otherwise, use the shared _cifsFileInfo_put(), like the mod_delayed_work() branch above: the pending execution already owns its reference.
This issue was found by an in-house static analysis tool.
Which versions are affected by CVE-2026-97558?
How do I fix CVE-2026-97558?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-97558 being exploited?
There is no known exploitation of CVE-2026-97558 in the wild and no public exploit code.
Sources
Also known as AZL-104175, BELL-CVE-2026-97558, DEBIAN-CVE-2026-97558, GHSA-25h5-cphg-25gg, UBUNTU-CVE-2026-97558.