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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
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.
Sources
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 and 1 more.