CVE-2026-31708: Linux Kernel

High severity, CVSS 8.1. EPSS: 0.6% chance of exploitation in the next 30 days.

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix OOB read in smb2_ioctl_query_info QUERY_INFO path smb2_ioctl_query_info() has two response-copy branches: PASSTHRU_FSCTL and the default QUERY_INFO path. The QUERY_INFO branch clamps qi.input_buffer_length to the server-reported OutputBufferLength and then copies qi.input_buffer_length bytes from qi_rsp->Buffer to userspace, but it never verifies that the flexible-array payload actually fits within rsp_iov[1].iov_len. A malicious server can return OutputBufferLength larger than the actual QUERY_INFO response, causing copy_to_user() to walk past the response buffer and expose adjacent kernel heap to userspace. Guard the QUERY_INFO copy with a bounds check on the actual Buffer payload. Use struct_size(qi_rsp, Buffer, qi.input_buffer_length) rather than an open-coded addition so the guard cannot overflow on 32-bit builds.

Affected products

• Linux Linux Kernel: from 5.1, before 6.6.136 (fixed in 6.6.136); from 6.7, before 6.12.84 (fixed in 6.12.84); from 6.13, before 6.18.25 (fixed in 6.18.25); from 6.19, before 7.0.2 (fixed in 7.0.2)

Published 2026-05-01. Last modified 2026-06-19.