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Vulnerability record · CVE-2026-31432 · published 22 April 2026

CVE-2026-31432: Linux kernel out-of-bounds write vulnerability

Linux · Linux Kernel

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.

8.8 CVSS 3.1 High EPSS 0.60% · top 53.4% CWE-787 · Out-of-bounds write
8.8CVSS 3.1 base score
0.60%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
5References
19 Jun 2026Last modified by NVD

Description

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.

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/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/075ea208c648cc2bcd616295b711d3637c61de45 Patch
https://git.kernel.org/stable/c/515c2daab46021221bdf406bef19bc90a44ec617 Patch
https://git.kernel.org/stable/c/850452af77f55d185f9445e1f7a1db53c5e4aad4
https://git.kernel.org/stable/c/d48c64fb80ad78b3dd29fb7d79b6ec7bd72bfc09 Patch
https://git.kernel.org/stable/c/fda9522ed6afaec45cabc198d8492270c394c7bc Patch

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Source: NIST National Vulnerability Database (record CVE-2026-31432), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.