---
id: CVE-2026-31432
title: 'ksmbd: fix OOB write in QUERY_INFO for compound requests'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ksmbd: fix OOB write in QUERY_INFO for compound requests

  When a compound request such as READ + QUERY_INFO(Security) is received,
  and the first command (READ) consumes…
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 9f297df20d93411c0b4ddad7f88ba04a7cd36e77 <
    533f84264e28c54a79257ea87d2f94a0fcc9a611
  - >-
    Linux >= e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d <
    850452af77f55d185f9445e1f7a1db53c5e4aad4
  - >-
    Linux >= e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d <
    d48c64fb80ad78b3dd29fb7d79b6ec7bd72bfc09
  - >-
    Linux >= e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d <
    075ea208c648cc2bcd616295b711d3637c61de45
  - >-
    Linux >= e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d <
    515c2daab46021221bdf406bef19bc90a44ec617
  - >-
    Linux >= e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d <
    fda9522ed6afaec45cabc198d8492270c394c7bc
  - Linux f2283680a80571ca82d710bc6ecd8f8beac67d63
  - Linux >= 6.1.71 < 6.1.191
  - Linux >= 5.15.145 < 5.16
  - Linux 6.6
published: '2026-04-22'
updated: '2026-10-30'
sourceUpdated: '2026-10-30T12:24:13.087Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-31432'
references:
  - url: 'https://git.kernel.org/stable/c/533f84264e28c54a79257ea87d2f94a0fcc9a611'
  - url: 'https://git.kernel.org/stable/c/850452af77f55d185f9445e1f7a1db53c5e4aad4'
  - url: 'https://git.kernel.org/stable/c/d48c64fb80ad78b3dd29fb7d79b6ec7bd72bfc09'
  - url: 'https://git.kernel.org/stable/c/075ea208c648cc2bcd616295b711d3637c61de45'
  - url: 'https://git.kernel.org/stable/c/515c2daab46021221bdf406bef19bc90a44ec617'
  - url: 'https://git.kernel.org/stable/c/fda9522ed6afaec45cabc198d8492270c394c7bc'
tags:
  - cve.org
epss: 0.00546
epssPercentile: 0.46068
ingestedAt: '2026-11-05T15:02:32.233Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: fix OOB write in QUERY_INFO for compound requests

When a compound request such as READ + QUERY_INFO(Security) is received,
and the first command (READ) consumes most of the response buffer,
ksmbd could write beyond the allocated buffer while building a security
descriptor.

The root cause was that smb2_get_info_sec() checked buffer space using
ppntsd_size from xattr, while build_sec_desc() often synthesized a
significantly larger descriptor from POSIX ACLs.

This patch introduces smb_acl_sec_desc_scratch_len() to accurately
compute the final descriptor size beforehand, performs proper buffer
checking with smb2_calc_max_out_buf_len(), and uses exact-sized
allocation + iov pinning.

## Affected

- `Linux >= 9f297df20d93411c0b4ddad7f88ba04a7cd36e77 < 533f84264e28c54a79257ea87d2f94a0fcc9a611`
- `Linux >= e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d < 850452af77f55d185f9445e1f7a1db53c5e4aad4`
- `Linux >= e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d < d48c64fb80ad78b3dd29fb7d79b6ec7bd72bfc09`
- `Linux >= e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d < 075ea208c648cc2bcd616295b711d3637c61de45`
- `Linux >= e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d < 515c2daab46021221bdf406bef19bc90a44ec617`
- `Linux >= e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d < fda9522ed6afaec45cabc198d8492270c394c7bc`
- `Linux f2283680a80571ca82d710bc6ecd8f8beac67d63`
- `Linux >= 6.1.71 < 6.1.191`
- `Linux >= 5.15.145 < 5.16`
- `Linux 6.6`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.