CVE-2026-90091
HighCVSS 8.0Exploitation Probability (EPSS)
Low risk29th percentile - higher than 29% of all known CVEs
Summary
A race condition exists in the Linux kernel Bluetooth L2CAP subsystem between l2cap_sock_cleanup_listen() and l2cap_sock_put_chan(). An unsynchronized read of the l2cap_pi(sk)->chan pointer may return NULL, leading to a null-ptr-deref and kernel crash. The issue is fixed by taking lock_sock() in l2cap_sock_kill().
Risk Assessment
The vulnerability can be exploited by a local attacker to cause a kernel crash (denial of service) or potentially escalate privileges. It affects systems with an active Bluetooth L2CAP stack.
Recommendation
Update the Linux kernel to a version containing the fix for CVE-2026-90091. If updating is not possible, consider disabling Bluetooth or restricting access to Bluetooth interfaces.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: fix race l2cap_sock_cleanup_listen() vs. put_chan For L2CAP sockets without owning sk->sk_socket, reading l2cap_pi(sk)->chan may race against concurrent l2cap_sock_kill() -> l2cap_sock_put_chan(). This excludes simultaneous proto_ops callbacks, but access in l2cap_sock_cleanup_listen() has unsafe lockless read. [Task 1] [Task 2 (hdev->workqueue)] l2cap_sock_release(parent) l2cap_disconn_cfm l2cap_sock_cleanup_listen l2cap_conn_del bt_accept_dequeue l2cap_chan_del lock_sock(sk) l2cap_sock_teardown_cb bt_accept_unlink bt_sk(sk)->parent = NULL release_sock(sk) ----------------> lock_sock(sk) parent = /* NULL */ lock_sock(sk) <--------------------- release_sock(sk) sock_set_flag(sk, SOCK_ZAPPED) l2cap_sock_close_cb l2cap_sock_kill(sk) l2cap_sock_put_chan chan = READ l2cap_pi(sk)->chan l2cap_pi(sk)->chan = NULL l2cap_chan_hold_unless_zero l2cap_put_chan(chan) kref_get_unless_zero(&chan->ref) Task 1 may observe NULL which causes null-ptr-deref. Fix the race by taking lock_sock() in l2cap_sock_kill() to synchronize with l2cap_sock_cleanup_listen(). hold_unless_zero() is not needed here, l2cap_pi(sk)->chan owns reference if it is non-NULL. Clarify code comments vs. locking.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS

