The Linux kernel SMB client had a vulnerability (CVE-2026-64257) related to the handling of overlapping data areas in SMB2 responses. A commit restricted the implied bcc[0] length exemption to responses without a data area, but the overlap handling function __smb2_calc_size() cleared data_length, making some invalid responses appear as if they had no data area and thus incorrectly qualifying for the exemption. The patch tracks data area overlap separately and rejects responses with overlapping data areas before applying length compatibility exceptions, preventing acceptance of malformed SMB2 responses.

The vulnerability could allow the Linux kernel SMB client to accept malformed SMB2 responses with overlapping data areas, potentially leading to incorrect processing of SMB data. The exact impact is not detailed in the provided information, and no known exploits in the wild have been reported.

A fix has been implemented in the Linux kernel to address this vulnerability by rejecting SMB2 responses with overlapping data areas before applying length compatibility exceptions. Users should update to the fixed Linux kernel version containing commit 53b7c271f06b or later. Patch status is not explicitly confirmed in the provided data; check the Linux kernel vendor advisory for the exact fixed versions and update guidance.