CVE-2026-90256 Bluetooth: L2CAP: use proto_lock for l2cap_data to fix l2cap_disconn_ind
A race condition in the Linux kernel Bluetooth L2CAP subsystem allows a use-after-free, potentially leading to code execution or privilege escalation.
- 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-2026-90256?
CVE-2026-90256 is a high-severity use after free vulnerability in Linux, published on 17 Sep 2026. 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: L2CAP: use proto_lock for l2cap_data to fix l2cap_disconn_ind
hci_conn::l2cap_data is accessed without locks in l2cap_disconn_ind via hci_conn_timeout (disc_work) -> hci_proto_disconn_ind -> l2cap_disconn_ind. This is UAF if the l2cap_conn is deleted concurrently.
disc_work is disabled sync in hci_conn_del(), so we cannot take hci_dev_lock in disc_work.
Fix by using proto_lock to guard l2cap_data, in addition to hdev->lock which is held in other access paths.
Which versions are affected by CVE-2026-90256?
How do I fix CVE-2026-90256?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-90256 being exploited?
There is no known exploitation of CVE-2026-90256 in the wild and no public exploit code.
Sources
Also known as AZL-101909, BELL-CVE-2026-90256, DEBIAN-CVE-2026-90256, GHSA-323m-rj3w-9jqp, UBUNTU-CVE-2026-90256.