# CVE-2025-39975: smb: client: fix wrong index reference in smb2_compound_op()

> A wrong index reference in the Linux kernel SMB client can cause out-of-bounds memory accesses, potentially leading to code execution or system crashes.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:** 15 Oct 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-39975, DEBIAN-CVE-2025-39975, GHSA-cm9p-f4x4-35gj, ROOT-OS-DEBIAN-13-CVE-2025-39975, UBUNTU-CVE-2025-39975

## What is CVE-2025-39975?

CVE-2025-39975 is a critical memory corruption vulnerability in Linux, published on 15 Oct 2025. 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: fix wrong index reference in smb2_compound_op()

In smb2_compound_op(), the loop that processes each command's response
uses wrong indices when accessing response bufferes.

This incorrect indexing leads to improper handling of command results.
Also, if incorrectly computed index is greather than or equal to
MAX_COMPOUND, it can cause out-of-bounds accesses.

## Which versions are affected by CVE-2025-39975?


## How do I fix CVE-2025-39975?

Apply the vendor's patch.

## Is CVE-2025-39975 being exploited?

There is no known exploitation of CVE-2025-39975 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-39975 and fix it if it is affected.

What it is: CVE-2025-39975 is a critical memory corruption vulnerability in Linux, published on 15 Oct 2025. 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-2025-39975 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-2025-39975/ (Markdown: https://insights.sbomify.com/CVE-2025-39975/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-39975
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-39975
- OSV: https://osv.dev/vulnerability/CVE-2025-39975

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-39975/
Summaries are generated and may contain mistakes; the official description above is the record.