# CVE-2026-64137: smb: client: require net admin for CIFS SWN netlink

> Unprivileged local processes can access sensitive CIFS witness data and send notifications due to missing capability checks in the Linux kernel SMB client.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 19 Jul 2026
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2026-64137, DEBIAN-CVE-2026-64137, GHSA-5vrr-7h3c-f6hv, ROOT-OS-UBUNTU-2204-CVE-2026-64137, UBUNTU-CVE-2026-64137

## What is CVE-2026-64137?

CVE-2026-64137 is a high-severity missing authorization vulnerability in Linux kernel, published on 19 Jul 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: require net admin for CIFS SWN netlink

CIFS_GENL_CMD_SWN_NOTIFY is the userspace witness-notify command.  The
intended sender is the cifs.witness helper, but the generic-netlink
operation currently has no capability flag, so any local process can send
RESOURCE_CHANGE or CLIENT_MOVE notifications to the in-kernel witness
handler.

The same family exposes CIFS_GENL_MCGRP_SWN without multicast-group
capability flags.  Register messages sent to that group include the witness
registration id and, for NTLM-authenticated mounts, the username, domain,
and password attributes copied from the CIFS session.  An unprivileged
local process should not be able to join that group and receive those
messages.

Require CAP_NET_ADMIN for incoming SWN_NOTIFY commands with
GENL_ADMIN_PERM, and require CAP_NET_ADMIN over the network namespace for
joining the SWN multicast group with GENL_MCAST_CAP_NET_ADMIN.  The
cifs.witness service runs with the privileges needed for both operations.

## Which versions are affected by CVE-2026-64137?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-64137?

Apply the vendor's patch.

## Is CVE-2026-64137 being exploited?

There is no known exploitation of CVE-2026-64137 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64137 and fix it if it is affected.

What it is: CVE-2026-64137 is a high-severity missing authorization vulnerability in Linux kernel, published on 19 Jul 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-2026-64137 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-64137/ (Markdown: https://insights.sbomify.com/CVE-2026-64137/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64137
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64137
- OSV: https://osv.dev/vulnerability/CVE-2026-64137

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64137/
Summaries are generated and may contain mistakes; the official description above is the record.