# 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.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-104175, BELL-CVE-2026-97558, DEBIAN-CVE-2026-97558, GHSA-25h5-cphg-25gg, UBUNTU-CVE-2026-97558

## 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.

## Is CVE-2026-97558 being exploited?

There is no known exploitation of CVE-2026-97558 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97558 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-97558 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-97558/ (Markdown: https://insights.sbomify.com/CVE-2026-97558/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97558
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97558
- OSV: https://osv.dev/vulnerability/CVE-2026-97558

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97558/
Summaries are generated and may contain mistakes; the official description above is the record.