# CVE-2026-64395: ksmbd: require source read access for duplicate extents

> An attacker can read file contents via duplicate extents without proper read access checks in the Linux kernel ksmbd module.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Jul 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-64395, DEBIAN-CVE-2026-64395, GHSA-33q2-xqvr-5v3j, ROOT-OS-DEBIAN-12-CVE-2026-64395, ROOT-OS-UBUNTU-2204-CVE-2026-64395, UBUNTU-CVE-2026-64395

## What is CVE-2026-64395?

CVE-2026-64395 is a high-severity missing authorization vulnerability in Linux kernel, published on 25 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

ksmbd: require source read access for duplicate extents

FSCTL_DUPLICATE_EXTENTS_TO_FILE passes the source file directly to
vfs_clone_file_range() or vfs_copy_file_range() without checking the SMB
access mask granted to the source handle. A handle opened with attribute
access can consequently be used to copy file contents into an
attacker-readable destination.

Require FILE_READ_DATA on the source handle before either VFS operation,
matching other ksmbd data-copy paths.

## Which versions are affected by CVE-2026-64395?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-64395?

Apply the vendor's patch.

## Is CVE-2026-64395 being exploited?

There is no known exploitation of CVE-2026-64395 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-2026-64395 and fix it if it is affected.

What it is: CVE-2026-64395 is a high-severity missing authorization vulnerability in Linux kernel, published on 25 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-64395 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-2026-64395/ (Markdown: https://insights.sbomify.com/CVE-2026-64395/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64395
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64395
- OSV: https://osv.dev/vulnerability/CVE-2026-64395

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64395/
Summaries are generated and may contain mistakes; the official description above is the record.