Zephyr Project up to 4.4.2 Bluetooth HCI USB Transport bt_hci.c bt_hci_tx_sync_in data/len buffer overflow

Summaryinfo

A vulnerability classified as very critical was found in Zephyr Project Zephyr up to 4.4.2. Affected by this issue is the function bt_hci_tx_sync_in of the file subsys/usb/device_next/class/bt_hci.c of the component Bluetooth HCI USB Transport. Such manipulation of the argument data/len leads to buffer overflow. This vulnerability is referenced as CVE-2026-79982. It is possible to launch the attack remotely. No exploit is available. It is advisable to implement a patch to correct this issue.

Detailsinfo

A vulnerability was found in Zephyr Project Zephyr up to 4.4.2 and classified as very critical. Affected by this issue is the function bt_hci_tx_sync_in of the file subsys/usb/device_next/class/bt_hci.c of the component Bluetooth HCI USB Transport. The manipulation of the argument data/len with an unknown input leads to a buffer overflow vulnerability. Using CWE to declare the problem leads to CWE-120. The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. Impacted is confidentiality, integrity, and availability. CVE summarizes:

The Bluetooth HCI USB transport class of the new USB device stack, subsys/usb/device_next/class/bt_hci.c, copies every controller-to-host HCI packet into a USB transfer buffer before enqueuing it on an endpoint. bt_hci_tx_sync_in() allocated that buffer from bt_hci_ep_pool, a fixed pool whose slots are only USBD_MAX_BULK_MPS bytes (64 on full-speed-only builds), and then performed net_buf_add_mem(buf, bt_buf->data, bt_buf->len) with no length check. HCI event and ACL buffers are sized by CONFIG_BT_BUF_EVT_RX_SIZE and CONFIG_BT_BUF_ACL_RX_SIZE and can be far larger, so the copy runs past the end of the 64-byte slot into the adjacent slots and into whatever follows the statically allocated pool. The device runs the local Bluetooth controller in raw HCI mode (CONFIG_BT_HCI_RAW), so the oversized packets originate over the air. With the HCI buffer sizes recommended for full-featured controllers, an unauthenticated attacker within Bluetooth range can supply the overflowing bytes: a connected peer that negotiates Data Length Extension can send ACL fragments up to CONFIG_BT_CTLR_DATA_LENGTH_MAX bytes, and an attacker that merely broadcasts extended advertising data reaches the same path through LE Extended Advertising Report events, which the controller fragments only to CONFIG_BT_BUF_EVT_RX_SIZE. In the stock configuration the overflow is already reached without any radio traffic: the mandatory Read Supported Commands command-complete event is 70 bytes and overruns the 64-byte slot by six bytes on every host initialization. Because net_buf_add_mem() validates tailroom only through an assertion unless CONFIG_NET_BUF_HARDENING is enabled, builds with CONFIG_ASSERT=n — the usual production setting — silently corrupt memory adjacent to the USB buffer pool with attacker-chosen contents, which on a target without memory protection between subsystems can lead to arbitrary code execution. Builds with assertions enabled fail the assertion instead and panic, giving a remotely triggerable denial of service. The fix introduces a separate bt_hci_tx_pool sized to MAX(BT_BUF_ACL_RX_SIZE, BT_BUF_EVT_RX_SIZE) for the controller-to-host direction while leaving the host-to-device pool at the endpoint packet size, which is already bounds-checked during reassembly.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-79982 since 08/25/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 10/23/2026).

Applying the patch 0419defd2391652edc27689d206fcd9c48439d4a is able to eliminate this problem.

Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

• Project Management Software

Vendor

• Zephyr Project

Name

• Zephyr

Version

• 4.4.0
• 4.4.1
• 4.4.2

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CPE 2.2info

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