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Vulnerability record · CVE-2026-31708 · published 1 May 2026

CVE-2026-31708: Linux kernel out-of-bounds read vulnerability

Linux · Linux Kernel

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.

8.1 CVSS 3.1 High EPSS 0.56% · top 55.4% CWE-125 · Out-of-bounds read
8.1CVSS 3.1 base score
0.56%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
8References
19 Jun 2026Last modified by NVD

Description

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://git.kernel.org/stable/c/078fae8f50adebb903ccf2252b44391324571e78 Patch
https://git.kernel.org/stable/c/1dd757379997b71a328a4b591ffaf481acd0ead1
https://git.kernel.org/stable/c/85fd46ee26a11841c670449508025965f61ce131 Patch
https://git.kernel.org/stable/c/9e203dbb5402897c43130fb171a2617008a91f45
https://git.kernel.org/stable/c/a34d456934fe42e4da5d2cc07787bf418bee99c6 Patch
https://git.kernel.org/stable/c/a58c5af19ff0d6f44f6e9fe31e33a2c92223f77e Patch
https://git.kernel.org/stable/c/ac2f14e4705d020f04e806efa0d49ab8dc2b145f Patch
https://git.kernel.org/stable/c/e66bdc0704977ecee667a81d38255b579c2353d0

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Source: NIST National Vulnerability Database (record CVE-2026-31708), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.