CVE-2026-31498

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> Bluetooth: L2CAP: Fix ERTM re-init and zero pdu_len infinite loop<br /> <br /> l2cap_config_req() processes CONFIG_REQ for channels in BT_CONNECTED<br /> state to support L2CAP reconfiguration (e.g. MTU changes). However,<br /> since both CONF_INPUT_DONE and CONF_OUTPUT_DONE are already set from<br /> the initial configuration, the reconfiguration path falls through to<br /> l2cap_ertm_init(), which re-initializes tx_q, srej_q, srej_list, and<br /> retrans_list without freeing the previous allocations and sets<br /> chan-&gt;sdu to NULL without freeing the existing skb. This leaks all<br /> previously allocated ERTM resources.<br /> <br /> Additionally, l2cap_parse_conf_req() does not validate the minimum<br /> value of remote_mps derived from the RFC max_pdu_size option. A zero<br /> value propagates to l2cap_segment_sdu() where pdu_len becomes zero,<br /> causing the while loop to never terminate since len is never<br /> decremented, exhausting all available memory.<br /> <br /> Fix the double-init by skipping l2cap_ertm_init() and<br /> l2cap_chan_ready() when the channel is already in BT_CONNECTED state,<br /> while still allowing the reconfiguration parameters to be updated<br /> through l2cap_parse_conf_req(). Also add a pdu_len zero check in<br /> l2cap_segment_sdu() as a safeguard.