EUVD-2026-18722
GHSA-ggw5-jw3c-r95v
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3Description
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: L2CAP: Fix use-after-free in l2cap_unregister_user
After commit ab4eedb790ca ("Bluetooth: L2CAP: Fix corrupted list in hci_chan_del"), l2cap_conn_del() uses conn->lock to protect access to conn->users. However, l2cap_register_user() and l2cap_unregister_user() don't use conn->lock, creating a race condition where these functions can access conn->users and conn->hchan concurrently with l2cap_conn_del().
This can lead to use-after-free and list corruption bugs, as reported by syzbot.
Fix this by changing l2cap_register_user() and l2cap_unregister_user() to use conn->lock instead of hci_dev_lock(), ensuring consistent locking for the l2cap_conn structure.
Analysis
Use-after-free in Linux kernel Bluetooth L2CAP layer allows local attackers to cause denial of service or potentially execute code via a race condition in l2cap_unregister_user(). The vulnerability arises because l2cap_register_user() and l2cap_unregister_user() access conn->users without proper locking (conn->lock), while l2cap_conn_del() protects the same structure with conn->lock, creating concurrent access to freed memory. …
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