# CVE-2026-64397: ksmbd: serialize QUERY_DIRECTORY requests per file

> Concurrent SMB directory queries can cause a stack use-after-free in the Linux kernel, potentially allowing local attackers to execute code or escalate privileges.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **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-2026-64397, DEBIAN-CVE-2026-64397, GHSA-76f2-j4c3-m5v4, ROOT-OS-DEBIAN-12-CVE-2026-64397, ROOT-OS-UBUNTU-2204-CVE-2026-64397, UBUNTU-CVE-2026-64397

## What is CVE-2026-64397?

CVE-2026-64397 is a critical use after free 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: serialize QUERY_DIRECTORY requests per file

smb2_query_dir() stores a pointer to its stack-allocated private data in
the ksmbd_file readdir_data. Concurrent QUERY_DIRECTORY requests using the
same file handle can overwrite this pointer while an iterate_dir() callback
is still using it, resulting in a stack use-after-free.

Add a per-file mutex and hold it while accessing the shared directory
enumeration state. The lock covers scan restart, dot entry state,
readdir_data setup and iteration, and response construction. This prevents
another request from replacing readdir_data.private before the current
request has finished using it and also serializes the shared file position.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-64397?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-64397?

Apply the vendor's patch.

## Is CVE-2026-64397 being exploited?

There is no known exploitation of CVE-2026-64397 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-2026-64397 and fix it if it is affected.

What it is: CVE-2026-64397 is a critical use after free 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-2026-64397 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-2026-64397/ (Markdown: https://insights.sbomify.com/CVE-2026-64397/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64397
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64397
- OSV: https://osv.dev/vulnerability/CVE-2026-64397

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64397/
Summaries are generated and may contain mistakes; the official description above is the record.