Incorrect Buffer Length Calculation in Linux Kernel ksmbd Component

Publication date: 2026-04-22

Last updated on: 2026-04-27

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: replace hardcoded hdr2_len with offsetof() in smb2_calc_max_out_buf_len() After this commit (e2b76ab8b5c9 "ksmbd: add support for read compound"), response buffer management was changed to use dynamic iov array. In the new design, smb2_calc_max_out_buf_len() expects the second argument (hdr2_len) to be the offset of ->Buffer field in the response structure, not a hardcoded magic number. Fix the remaining call sites to use the correct offsetof() value.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-04-22

Last Modified

2026-04-27

Generated

2026-07-06

AI Q&A

2026-04-22

EPSS Evaluated

2026-07-05

NVD

CVE-2026-31478

EUVD

EUVD-2026-24835

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	6.6
linux	linux_kernel	7.0
linux	linux_kernel	7.0
linux	linux_kernel	7.0
linux	linux_kernel	7.0
linux	linux_kernel	7.0
linux	linux_kernel	7.0
linux	linux_kernel	7.0
linux	linux_kernel	From 6.13 (inc) to 6.18.21 (exc)
linux	linux_kernel	From 6.19 (inc) to 6.19.11 (exc)
linux	linux_kernel	From 6.7 (inc) to 6.12.80 (exc)
linux	linux_kernel	From 5.15.145 (inc) to 5.15.203 (exc)
linux	linux_kernel	From 6.1.71 (inc) to 6.1.168 (exc)
linux	linux_kernel	From 6.6.1 (inc) to 6.6.131 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability relates to the Linux kernel's ksmbd component, specifically in the smb2_calc_max_out_buf_len() function. After a code change introduced support for read compound operations, the way response buffers were managed was altered to use a dynamic iov array. However, the function smb2_calc_max_out_buf_len() was still using a hardcoded value for hdr2_len, which should instead be the offset of the Buffer field within the response structure. This mismatch could lead to incorrect buffer length calculations. The vulnerability was fixed by replacing the hardcoded hdr2_len with the correct offsetof() value.

Impact Analysis

This vulnerability relates to incorrect handling of the response buffer length in the ksmbd component of the Linux kernel. If exploited, it could potentially lead to improper buffer management, which might cause unexpected behavior such as crashes or memory corruption.

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