# CVE-2026-97564: smb: client: reject userspace cifs.idmap descriptions

> Local attackers can exploit missing validation in the Linux kernel SMB client to trigger a root-context upcall, leading to privilege escalation.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-104379, BELL-CVE-2026-97564, DEBIAN-CVE-2026-97564, GHSA-3fc8-28wq-wq67, UBUNTU-CVE-2026-97564

## What is CVE-2026-97564?

CVE-2026-97564 is a 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: reject userspace cifs.idmap descriptions

cifs.idmap key descriptions carry authority-bearing fields (owner and
group SIDs and uid/gid values in "os:"/"gs:"/"oi:"/"gi:" form) that the
cifs.idmap upcall helper treats as kernel-originating inputs.  Unlike
its sibling cifs.spnego, the cifs.idmap key type has no vet_description
hook, so userspace can create keys of this type through
request_key(2)/add_key(2) and supply those fields without CIFS origin.
A request_key(2) call with a non-NULL callout then drives a root
usermodehelper upcall (/sbin/request-key -> cifs.idmap) that consumes
the unvetted description in root context.

Only accept cifs.idmap descriptions while CIFS is using its private
root_cred to request the key.  id_to_sid()/sid_to_id() already run
under override_creds(root_cred), so the kernel-originated path is
unaffected.

This mirrors commit 3da1fdf4efbc ("smb: client: reject userspace
cifs.spnego descriptions"), which applied the same restriction to
cifs.spnego.

## Which versions are affected by CVE-2026-97564?


## How do I fix CVE-2026-97564?

Apply the vendor's patch.

## Is CVE-2026-97564 being exploited?

There is no known exploitation of CVE-2026-97564 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97564 and fix it if it is affected.

What it is: CVE-2026-97564 is a 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-2026-97564 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-2026-97564/ (Markdown: https://insights.sbomify.com/CVE-2026-97564/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97564
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97564
- OSV: https://osv.dev/vulnerability/CVE-2026-97564

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97564/
Summaries are generated and may contain mistakes; the official description above is the record.