# CVE-2026-31717: ksmbd: validate owner of durable handle on reconnect

> An authenticated user can hijack orphaned durable file handles in the Linux kernel ksmbd server, allowing unauthorized access to files opened by other users.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/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:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 May 2026
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2026-31717, DEBIAN-CVE-2026-31717, GHSA-ffmp-v5q6-mvpq, ROOT-OS-DEBIAN-13-CVE-2026-31717, UBUNTU-CVE-2026-31717

## What is CVE-2026-31717?

CVE-2026-31717 is a high-severity missing authorization vulnerability in Linux kernel, published on 1 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

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

ksmbd: validate owner of durable handle on reconnect

Currently, ksmbd does not verify if the user attempting to reconnect
to a durable handle is the same user who originally opened the file.
This allows any authenticated user to hijack an orphaned durable handle
by predicting or brute-forcing the persistent ID.

According to MS-SMB2, the server MUST verify that the SecurityContext
of the reconnect request matches the SecurityContext associated with
the existing open.
Add a durable_owner structure to ksmbd_file to store the original opener's
UID, GID, and account name. and catpure the owner information when a file
handle becomes orphaned. and implementing ksmbd_vfs_compare_durable_owner()
to validate the identity of the requester during SMB2_CREATE (DHnC).

## Which versions are affected by CVE-2026-31717?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31717?

Apply the vendor's patch.

## Is CVE-2026-31717 being exploited?

There is no known exploitation of CVE-2026-31717 in the wild and no public exploit code.

Public exploit code:

- ksmbd CVEs: CVE-2026-31717, CVE-2026-68083 (github_poc): https://github.com/TurtleARM/ksmbrace

## 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-2026-31717 and fix it if it is affected.

What it is: CVE-2026-31717 is a high-severity missing authorization vulnerability in Linux kernel, published on 1 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-31717 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-2026-31717/ (Markdown: https://insights.sbomify.com/CVE-2026-31717/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31717
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31717
- OSV: https://osv.dev/vulnerability/CVE-2026-31717

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31717/
Summaries are generated and may contain mistakes; the official description above is the record.