# CVE-2026-90156: ksmbd: safely discard unregistered deferred locks

> A null pointer dereference in the Linux kernel ksmbd module allows remote attackers to cause a denial of service via crafted SMB2 lock requests.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-102651, BELL-CVE-2026-90156, DEBIAN-CVE-2026-90156, GHSA-7qq9-mrjw-5hqq, UBUNTU-CVE-2026-90156

## What is CVE-2026-90156?

CVE-2026-90156 is a vulnerability in Linux, published on 17 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: safely discard unregistered deferred locks

When vfs_lock_file() defers a lock, smb2_lock() puts its ksmbd_lock on
rollback_list before allocating and registering the asynchronous work.
If either operation fails, rollback assumes that smb_lock->conn is
initialized and dereferences NULL. The deferred file_lock also remains
linked into the VFS blocked-lock state while it is freed.

Keep the lock off rollback_list until async setup succeeds. On setup
failures, explicitly unblock and wake the deferred lock before freeing it
and its ksmbd wrapper.

## Which versions are affected by CVE-2026-90156?


## How do I fix CVE-2026-90156?

Apply the vendor's patch.

## Is CVE-2026-90156 being exploited?

There is no known exploitation of CVE-2026-90156 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90156 and fix it if it is affected.

What it is: CVE-2026-90156 is a vulnerability in Linux, published on 17 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-90156 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-2026-90156/ (Markdown: https://insights.sbomify.com/CVE-2026-90156/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90156
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90156
- OSV: https://osv.dev/vulnerability/CVE-2026-90156

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90156/
Summaries are generated and may contain mistakes; the official description above is the record.