CVE-2026-19738
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
Impact
Nearby attackers within Bluetooth radio range can crash or freeze the device by sending malformed Link Layer control packets. No pairing, authentication, or user interaction is required.
Root cause
The Bluetooth Link Layer ISO stream creation procedure terminates error paths without releasing a retained RX node, causing fatal assertion crashes or memory exhaustion.
Affected systems
Zephyr RTOS builds with CONFIG_BT_CTLR_PERIPHERAL_ISO or CONFIG_BT_CTLR_CENTRAL_ISO enabled (specific version numbers 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 fde17f2c3de0118f3796c2a83958ee4ce4b5efd6 from upstream Zephyr. If patching must wait, disable CONFIG_BT_CTLR_PERIPHERAL_ISO and CONFIG_BT_CTLR_CENTRAL_ISO in your project configuration.
AI-suggested. Run it in staging first and check it against the vendor advisory. Why?
NVD description
The Bluetooth Link Layer Control Procedure (LLCP) implementation for Connected Isochronous Stream (CIS) creation retains an RX node (ctx->node_ref.rx, marked NODE_RX_TYPE_RETAIN) so it can later be reused as the host notification — on the peripheral while awaiting the Host's reply to an LL_CIS_REQ, and on the central for the whole duration of a locally initiated CIS Create. In subsys/bluetooth/controller/ll_sw/ull_llcp_cc.c, the "invalid PDU received" paths of llcp_rp_cc_rx() and llcp_lp_cc_rx() terminated the connection and completed the procedure without releasing that retained node, breaking the invariant checked in llcp_lr_check_done() and llcp_rr_check_done() and orphaning the node's memory. A peer device within radio range can reach this with a single extra LL Control PDU on an unauthenticated, unencrypted ACL link. Against a peripheral, the attacker sends a valid LL_CIS_REQ and then, before the Host replies, any unrelated LL Control PDU (for example LL_VERSION_IND), which ull_cp_rx() routes into the active remote procedure. Against a central performing a CIS Create, a malicious peripheral answers with LL_UNKNOWN_RSP for CIS_REQ, which is dispatched into the active local procedure. No pairing, encryption or user interaction is required; the code is compiled in when CONFIG_BT_CTLR_PERIPHERAL_ISO or CONFIG_BT_CTLR_CENTRAL_ISO is enabled. In default builds (CONFIG_BT_CTLR_ASSERT_DEBUG is default y) the retained-node assertion fires immediately, producing a controller fatal error and, typically, a system reset from one injected PDU. With the development assertions disabled, each attempt permanently loses one node from the controller's small LL notification pool (LL_PDU_RX_CNT, 2 * CONFIG_BT_CTLR_LLCP_CONN) together with its memq_link_t; repeating the connect-attack-reconnect cycle exhausts the pool, after which notification allocation always fails, RX flow control stalls, and the non-disableable LL_ASSERT_ERR() in llcp_lp_cc_flush() faults. The impact is limited to availability — the leaked node is orphaned, never reused or double-freed — and recovery requires a reboot.