Zephyr Project up to 4.4.x Bluetooth Host ATT Layer att.c bt_att_released att_chan/reqs use after free

Summaryinfo

A vulnerability identified as very critical has been detected in Zephyr Project Zephyr up to 4.4.x. Affected is the function bt_att_released of the file subsys/bluetooth/host/att.c of the component Bluetooth Host ATT Layer. The manipulation of the argument att_chan/reqs leads to use after free. This vulnerability is referenced as CVE-2026-11368. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability was found in Zephyr Project Zephyr up to 4.4.x and classified as very critical. This issue affects the function bt_att_released of the file subsys/bluetooth/host/att.c of the component Bluetooth Host ATT Layer. The manipulation of the argument att_chan/reqs with an unknown input leads to a use after free vulnerability. Using CWE to declare the problem leads to CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

The Bluetooth host ATT layer (subsys/bluetooth/host/att.c) associates each in-flight ATT TX buffer with its owning channel via the static tx_meta_data_storage[] array (data->att_chan = chan). When a buffer's last reference is dropped, its net-buf destroy callback defers the completion handling to the system workqueue (att_tx_destroy -> att_tx_destroy_work_handler -> att_on_sent_cb -> bt_att_sent), where bt_att_sent dereferences the channel and its ATT context (sys_slist_get(&att->reqs)). When a peer disconnects while an ATT PDU (a server notification/indication or any response) is still in flight in the controller TX path, L2CAP tears the channel down in l2cap_chan_del(): it runs the disconnected callback and then the released callback (bt_att_released), which frees the channel slab slot. Because the in-flight buffer is held by the connection TX path rather than the channel's own queue, its deferred destroy work can run after the channel has been freed. The att_on_sent_cb guard intended to drop the stale callback itself dereferences meta->att_chan, which is now a dangling pointer into a freed (and possibly reused) slab slot. A remote peer with an ATT connection can drive this by disconnecting during routine ATT traffic; no pairing or user interaction is required to reach the ATT bearer. The result is a use-after-free read/write of freed channel memory, reliably crashing the Bluetooth host (denial of service) and, because the channel slab slot may be reused, potentially corrupting live memory. The fix makes bt_att_released() NULL the att_chan field of every tx_meta_data_storage[] entry still referencing the channel before freeing it, so the deferred guard observes a NULL pointer and drops the callback. Teardown and the destroy work both run on the cooperative system workqueue, so the array update is serialized and needs no lock.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-11368 since 06/05/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/04/2026).

Upgrading to version 4.5.0 eliminates this vulnerability. Applying the patch dfdea9bad8d9b5b31c125e97fcffb549f2217caa is able to eliminate this problem.

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Productinfo

Type

• Project Management Software

Vendor

• Zephyr Project

Name

• Zephyr

Version

• 4.0
• 4.1
• 4.2
• 4.3
• 4.4

CPE 2.3info

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CPE 2.2info

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