CVE-2026-19739
6.5MediumPublished 11 Oct 2026 · NVD status: Awaiting Analysis · AI triage by gemini-3.8-flash
- Attack vector
- Adjacent network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
- Impact
- High impact on availability
- Weakness
- CWE-401, CWE-459, CWE-617, CWE-772
Impact
Unauthenticated attackers within Bluetooth radio range can crash the controller or exhaust link-layer buffers, causing a persistent denial of service until reboot. They do not need pairing, bonding, or encryption.
Root cause
The Bluetooth Link Layer error-handling path for invalid PDUs completes Connection Update procedures without releasing retained RX nodes, causing an assertion failure or leaking fixed buffer pool memory.
Affected systems
Zephyr RTOS versions containing the ll_sw controller implementation (exact release versions not listed — check the vendor advisory).
CVSS v3.1 · CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Fix & remediation
Apply commit 7b600129faaba8bb26dd5cb3e8f17ed1cb41ea7f to your Zephyr build tree and reflash firmware; no interim configuration mitigation is available.
AI-suggested. Run it in staging first and check it against the vendor advisory. Why?
NVD description
The Bluetooth Link Layer control procedure code in subsys/bluetooth/controller/ll_sw/ull_llcp_conn_upd.c retains the received RX node while a Connection Update / Connection Parameter procedure waits for its instant, so the node can later carry the host notification (llcp_rx_node_retain(), which marks it NODE_RX_TYPE_RETAIN and thereby suppresses the normal recycling in ull.c). The default: arm of llcp_rp_cu_rx() and llcp_lp_cu_rx() — the "invalid PDU, terminate the connection" path — completed the procedure without releasing that retained node. llcp_rr_check_done() then dequeued and freed the procedure context with ctx->node_ref.rx still pointing at the retained node, dropping the last reference to it. A peer device in radio range can reach this without pairing, bonding, or encryption. Against a peripheral, the peer sends a well-formed LL_CONNECTION_UPDATE_IND with an instant a few connection events in the future (the node is retained and the procedure enters RP_CU_STATE_WAIT_INSTANT), then, before the instant is reached, sends any other LL Control PDU such as LL_LENGTH_REQ. ull_cp_rx() routes that PDU into the active remote Connection Update procedure, which takes the invalid-PDU path. The central role is reachable symmetrically after accepting an LL_CONNECTION_PARAM_REQ, and the local-procedure variant is reachable with LL_REJECT_IND. With CONFIG_BT_CTLR_ASSERT_DEBUG enabled (its default), the resulting state violates the invariant asserted in llcp_rr_check_done(), so the two-PDU sequence produces an immediate fatal error in the controller. With those asserts disabled, each occurrence permanently loses one node from the controller's small fixed RX pool (sized from CONFIG_BT_CTLR_RX_BUFFERS, which defaults to 1); repeating the sequence across reconnections exhausts the pool, after which the link-layer receive path operates on a NULL node. The impact is an unauthenticated, remotely triggerable denial of service persisting until reboot; there is no memory-disclosure or memory-corruption consequence, since the leaked node simply becomes unreachable.