CVE-2026-31498

Technical Description

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_er

Remediation

Check the references section for vendor advisories and patches from linux. Update linux_kernel to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected Products

References