# CVE-2026-64140: ksmbd: fix null pointer dereference in proc_show_files()

> A local attacker can crash the Linux kernel by reading a proc file while a durable SMB2 handle is disconnected, causing a null pointer dereference.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:** 19 Jul 2026
- **Updated:** 5 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-64140, GHSA-3wf5-rcm5-gfqq, UBUNTU-CVE-2026-64140

## What is CVE-2026-64140?

CVE-2026-64140 is a high-severity vulnerability in Linux kernel, published on 19 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: fix null pointer dereference in proc_show_files()

When a SMB2 client opens a file with a durable v2 handle and then issues
SMB2 SESSION_LOGOFF, session_fd_check() clears fp->tcon = NULL on the
reconnectable file pointer but leaves the fp registered in global_ft.idr
until the durable scavenger fires (up to fp->durable_timeout seconds
later).

During that window any read of /proc/fs/ksmbd/files (mode 0400) panics
the kernel because proc_show_files() walks global_ft.idr and
unconditionally dereferences fp->tcon->id with no NULL guard.

Reproducer requires only a successful SMB2 SESSION_SETUP and a share
configured with 'durable handles = yes'. KASAN report on mainline
70390501d194:

  general protection fault, probably for non-canonical address
  0xdffffc0000000000: 0000 [#1] SMP KASAN PTI
  KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
  RIP: 0010:proc_show_files+0x118/0x740
  Call Trace:
   proc_show_files+0x118/0x740
   seq_read_iter+0x4ef/0xe10
   proc_reg_read_iter+0x1b7/0x280
   ...

Guard the dereference. A durable-disconnected fp legitimately has no
tcon; report its tree id as 0 rather than oopsing.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-64140?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-64140?

Apply the vendor's patch.

## Is CVE-2026-64140 being exploited?

There is no known exploitation of CVE-2026-64140 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-2026-64140 and fix it if it is affected.

What it is: CVE-2026-64140 is a high-severity vulnerability in Linux kernel, published on 19 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-2026-64140 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-2026-64140/ (Markdown: https://insights.sbomify.com/CVE-2026-64140/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64140
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64140
- OSV: https://osv.dev/vulnerability/CVE-2026-64140

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64140/
Summaries are generated and may contain mistakes; the official description above is the record.