# CVE-2026-64257: smb: client: reject overlapping data areas in SMB2 responses

> A flaw in the Linux kernel SMB client allows attackers to trigger memory corruption via overlapping data areas in SMB2 responses, potentially leading to code execution or privilege escalation.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/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:** 25 Jul 2026
- **Updated:** 17 Aug 2026
- **Also known as:** GHSA-cfrm-7rjv-hj84, ROOT-OS-UBUNTU-2204-CVE-2026-64257, UBUNTU-CVE-2026-64257

## What is CVE-2026-64257?

CVE-2026-64257 is a critical memory corruption 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:

smb: client: reject overlapping data areas in SMB2 responses

Commit 53b7c271f06b ("smb: client: restrict implied bcc[0] exemption to
responses without data area") restricted the implied bcc[0] length
exception to responses without a data area. However, the overlap
handling in __smb2_calc_size() clears data_length, which can make an
invalid response appear to have no data area and so qualify for the
exception.

Track data area overlap separately and reject such responses before
applying the length compatibility exceptions.

## Which versions are affected by CVE-2026-64257?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-64257?

Apply the vendor's patch.

## Is CVE-2026-64257 being exploited?

There is no known exploitation of CVE-2026-64257 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-2026-64257 and fix it if it is affected.

What it is: CVE-2026-64257 is a critical memory corruption 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-2026-64257 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-2026-64257/ (Markdown: https://insights.sbomify.com/CVE-2026-64257/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64257
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64257
- OSV: https://osv.dev/vulnerability/CVE-2026-64257

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64257/
Summaries are generated and may contain mistakes; the official description above is the record.