CVE-2026-31478

ksmbd: replace hardcoded hdr2_len with offsetof() in smb2_calc_max_out_buf_len()

State: Published
Severity: 9.8 Critical
Published: Apr 22, 2026
Updated: Oct 19, 2026
Reserved: Mar 9, 2026

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.

Scores

CVSS	Score	Vector	Source
3.1	9.8 Critical	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H	Linux

Weaknesses

CWE-131 Incorrect Calculation of Buffer Size

Affected Products

Product	Versions
LinuxLinux	f2283680a80571ca82d710bc6ecd8f8beac67d63 to before 70b4c414889492c522b6e4331562360f49be2361Affected 9f297df20d93411c0b4ddad7f88ba04a7cd36e77 to before 9a7166f0ef8cbb7bb48dd05e2471d995566003f5Affected e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d to before c3a89e3ec1ccf64fa6a34e391e1581ebbcba8683Affected e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d to before 6aef1765d6807e0f027cd87f6ac973eb0879a46dAffected e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d to before 80824c7e527b70cf9039534e60aff592e8f209d1Affected e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d to before 4cb537ae4f37d7d0f617815ed4bed7173fb50861Affected e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d to before 0e55f63dd08f09651d39e1b709a91705a8a0ddcbAffected 5.15.145 to before 5.15.203Affected 6.1.71 to before 6.1.168Affected
LinuxLinux	6.6Affected before 6.6Not affected 5.15.203 through 5.15.Not affected 6.1.168 through 6.1.Not affected 6.6.131 through 6.6.Not affected 6.12.80 through 6.12.Not affected 6.18.21 through 6.18.Not affected 6.19.11 through 6.19.Not affected 7.0 and laterNot affected

Product

Versions

LinuxLinux

f2283680a80571ca82d710bc6ecd8f8beac67d63 to before 70b4c414889492c522b6e4331562360f49be2361Affected
9f297df20d93411c0b4ddad7f88ba04a7cd36e77 to before 9a7166f0ef8cbb7bb48dd05e2471d995566003f5Affected
e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d to before c3a89e3ec1ccf64fa6a34e391e1581ebbcba8683Affected
e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d to before 6aef1765d6807e0f027cd87f6ac973eb0879a46dAffected
e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d to before 80824c7e527b70cf9039534e60aff592e8f209d1Affected
e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d to before 4cb537ae4f37d7d0f617815ed4bed7173fb50861Affected
e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d to before 0e55f63dd08f09651d39e1b709a91705a8a0ddcbAffected
5.15.145 to before 5.15.203Affected
6.1.71 to before 6.1.168Affected

LinuxLinux

6.6Affected
before 6.6Not affected
5.15.203 through 5.15.*Not affected
6.1.168 through 6.1.*Not affected
6.6.131 through 6.6.*Not affected
6.12.80 through 6.12.*Not affected
6.18.21 through 6.18.*Not affected
6.19.11 through 6.19.*Not affected
7.0 and laterNot affected

References

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