# CVE-2026-31433: ksmbd: fix potencial OOB in get_file_all_info() for compound requests

> A missing buffer length check in the Linux kernel ksmbd module allows out-of-bounds writes during compound SMB requests, potentially leading to memory corruption or crashes.

- **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:** 22 Apr 2026
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2026-31433, DEBIAN-CVE-2026-31433, GHSA-32xq-pcg8-hc33, ROOT-OS-DEBIAN-12-CVE-2026-31433, ROOT-OS-UBUNTU-2204-CVE-2026-31433, ROOT-OS-UBUNTU-2404-CVE-2026-31433, UBUNTU-CVE-2026-31433

## What is CVE-2026-31433?

CVE-2026-31433 is a high-severity memory corruption vulnerability in Linux kernel, published on 22 Apr 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: fix potencial OOB in get_file_all_info() for compound requests

When a compound request consists of QUERY_DIRECTORY + QUERY_INFO
(FILE_ALL_INFORMATION) and the first command consumes nearly the entire
max_trans_size, get_file_all_info() would blindly call smbConvertToUTF16()
with PATH_MAX, causing out-of-bounds write beyond the response buffer.
In get_file_all_info(), there was a missing validation check for
the client-provided OutputBufferLength before copying the filename into
FileName field of the smb2_file_all_info structure.
If the filename length exceeds the available buffer space, it could lead to
potential buffer overflows or memory corruption during smbConvertToUTF16
conversion. This calculating the actual free buffer size using
smb2_calc_max_out_buf_len() and returning -EINVAL if the buffer is
insufficient and updating smbConvertToUTF16 to use the actual filename
length (clamped by PATH_MAX) to ensure a safe copy operation.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-31433?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31433?

Apply the vendor's patch.

## Is CVE-2026-31433 being exploited?

There is no known exploitation of CVE-2026-31433 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-2026-31433 and fix it if it is affected.

What it is: CVE-2026-31433 is a high-severity memory corruption vulnerability in Linux kernel, published on 22 Apr 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-2026-31433 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-2026-31433/ (Markdown: https://insights.sbomify.com/CVE-2026-31433/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31433
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31433
- OSV: https://osv.dev/vulnerability/CVE-2026-31433

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31433/
Summaries are generated and may contain mistakes; the official description above is the record.