CVE-2026-63976 Bluetooth: l2cap: clear chan->ident on ECRED reconfiguration success
A remote attacker can cause a denial of service by replaying a failure response with a stale identifier, leading to the destruction of an established Bluetooth channel.
- 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-2026-63976?
CVE-2026-63976 is a high-severity denial of service vulnerability in Linux, published on 19 Jul 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: clear chan->ident on ECRED reconfiguration success
l2cap_ecred_reconf_rsp() returns early on success without clearing chan->ident. Every other L2CAP response handler (l2cap_ecred_conn_rsp, l2cap_le_connect_rsp, l2cap_config_rsp) clears chan->ident after a successful transaction to prevent the channel from matching subsequent responses with the recycled ident value.
A remote attacker that completed a reconfiguration as the peer can replay a failure response with the stale ident, causing the kernel to match and destroy the already-established channel via l2cap_chan_del(chan, ECONNRESET).
Clear chan->ident for all matching channels on success, and harden the failure path by using l2cap_chan_hold_unless_zero() consistent with other L2CAP handlers (l2cap_le_command_rej, __l2cap_get_chan_by_ident).
Weakness: CWE-694
Which versions are affected by CVE-2026-63976?
How do I fix CVE-2026-63976?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-63976 being exploited?
There is no known exploitation of CVE-2026-63976 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-63976, DEBIAN-CVE-2026-63976, GHSA-2c97-7qvf-wx4v, ROOT-OS-UBUNTU-2204-CVE-2026-63976, UBUNTU-CVE-2026-63976.