# CVE-2025-40301: Bluetooth: hci_event: validate skb length for unknown CC opcode

> A missing length check in the Linux kernel Bluetooth driver allows attackers to trigger a null dereference, causing a system crash.

- **Severity:** High 7.6 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 Dec 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-40301, DEBIAN-CVE-2025-40301, GHSA-mp66-rx49-f278, ROOT-OS-DEBIAN-12-CVE-2025-40301, ROOT-OS-DEBIAN-13-CVE-2025-40301, ROOT-OS-UBUNTU-2404-CVE-2025-40301, UBUNTU-CVE-2025-40301

## What is CVE-2025-40301?

CVE-2025-40301 is a high-severity vulnerability in Linux, published on 8 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

Bluetooth: hci_event: validate skb length for unknown CC opcode

In hci_cmd_complete_evt(), if the command complete event has an unknown
opcode, we assume the first byte of the remaining skb->data contains the
return status. However, parameter data has previously been pulled in
hci_event_func(), which may leave the skb empty. If so, using skb->data[0]
for the return status uses un-init memory.

The fix is to check skb->len before using skb->data.

## Which versions are affected by CVE-2025-40301?


## How do I fix CVE-2025-40301?

Apply the vendor's patch.

## Is CVE-2025-40301 being exploited?

There is no known exploitation of CVE-2025-40301 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40301 and fix it if it is affected.

What it is: CVE-2025-40301 is a high-severity vulnerability in Linux, published on 8 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-40301 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-2025-40301/ (Markdown: https://insights.sbomify.com/CVE-2025-40301/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40301
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40301
- OSV: https://osv.dev/vulnerability/CVE-2025-40301

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40301/
Summaries are generated and may contain mistakes; the official description above is the record.