# CVE-2026-72310: smb: client: fix overflow in passthrough ioctl bounds check

> A malicious SMB server can trigger an integer overflow in the Linux kernel client, leading to out-of-bounds memory reads and potential information disclosure.

- **Severity:** High 8.1 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/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:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** BELL-CVE-2026-72310, DEBIAN-CVE-2026-72310, GHSA-h4wv-r484-2rg5, UBUNTU-CVE-2026-72310

## What is CVE-2026-72310?

CVE-2026-72310 is a high-severity vulnerability in Linux, published on 15 Aug 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:

smb: client: fix overflow in passthrough ioctl bounds check

smb2_ioctl_query_info() validates the PASSTHRU_FSCTL response payload
before copying it to userspace.

The payload offset and length both come from 32-bit fields. The bounds
check currently adds OutputOffset and qi.input_buffer_length directly, so
the addition can wrap in 32-bit arithmetic before the result is compared
against the response buffer length.

A malicious server can use a large OutputOffset and a small OutputCount
to make the wrapped sum pass the bounds check. The later copy_to_user()
then reads from io_rsp + OutputOffset, outside the response buffer.

Use size_add() for the offset plus length check so overflow is treated as
out of bounds.

## Which versions are affected by CVE-2026-72310?


## How do I fix CVE-2026-72310?

Apply the vendor's patch.

## Is CVE-2026-72310 being exploited?

There is no known exploitation of CVE-2026-72310 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72310 and fix it if it is affected.

What it is: CVE-2026-72310 is a high-severity vulnerability in Linux, published on 15 Aug 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-2026-72310 in the wild and no public exploit code.

Affected product: Linux. 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-2026-72310/ (Markdown: https://insights.sbomify.com/CVE-2026-72310/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72310
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72310
- OSV: https://osv.dev/vulnerability/CVE-2026-72310

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72310/
Summaries are generated and may contain mistakes; the official description above is the record.