CVE-2026-31498

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

• linux linux kernel (>= 4.4.238 < 4.5) • linux linux kernel (>= 4.9.238 < 4.10) • linux linux kernel (>= 4.14.200 < 4.15) • linux linux kernel (>= 4.19.149 < 4.20) • linux linux kernel (>= 5.4.69 < 5.5) • linux linux kernel (>= 5.7.1 < 5.10.253) • linux linux kernel (>= 5.11 < 5.15.203) • linux linux kernel (>= 5.16 < 6.1.168) • linux linux kernel (>= 6.2 < 6.6.131) • linux linux kernel (>= 6.7 < 6.12.80) • linux linux kernel (>= 6.13 < 6.18.21) • linux linux kernel (>= 6.19 < 6.19.11) • linux linux kernel 5.7 • linux linux kernel 7.0