ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment

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Summary

CVECVE-2026-31705
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-01 14:16:20 UTC
Updated2026-05-03 07:16:17 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment smb2_get_ea() applies 4-byte alignment padding via memset() after writing each EA entry. The bounds check on buf_free_len is performed before the value memcpy, but the alignment memset fires unconditionally afterward with no check on remaining space. When the EA value exactly fills the remaining buffer (buf_free_len == 0 after value subtraction), the alignment memset writes 1-3 NUL bytes past the buf_free_len boundary. In compound requests where the response buffer is shared across commands, the first command (e.g., READ) can consume most of the buffer, leaving a tight remainder for the QUERY_INFO EA response. The alignment memset then overwrites past the physical kvmalloc allocation into adjacent kernel heap memory. Add a bounds check before the alignment memset to ensure buf_free_len can accommodate the padding bytes. This is the same bug pattern fixed by commit beef2634f81f ("ksmbd: fix potencial OOB in get_file_all_info() for compound requests") and commit fda9522ed6af ("ksmbd: fix OOB write in QUERY_INFO for compound requests"), both of which added bounds checks before unconditional writes in QUERY_INFO response handlers.

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

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

EPSS: 0.000180000 probability, percentile 0.048520000 (date 2026-05-02)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d ffbce350c6fd1e99116ea57383b9031717e36d3b git Not specified
CNA Linux Linux affected e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d 98f3de6ef4efbd899348d333f0902dc4ff14380c git Not specified
CNA Linux Linux affected e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d 790304c02bf9bd7b8171feda4294d6e62d32ae8f git Not specified
CNA Linux Linux affected e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d 922d48fe8c19f388ffa2f709f33acaae4e408de2 git Not specified
CNA Linux Linux affected e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d 30010c952077a1c89ecdd71fc4d574c75a8f5617 git Not specified
CNA Linux Linux affected f2283680a80571ca82d710bc6ecd8f8beac67d63 git Not specified
CNA Linux Linux affected 9f297df20d93411c0b4ddad7f88ba04a7cd36e77 git Not specified
CNA Linux Linux affected 6.6 Not specified
CNA Linux Linux unaffected 6.6 semver Not specified
CNA Linux Linux unaffected 6.6.136 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.84 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.25 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.2 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/790304c02bf9bd7b8171feda4294d6e62d32ae8f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/98f3de6ef4efbd899348d333f0902dc4ff14380c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/922d48fe8c19f388ffa2f709f33acaae4e408de2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/30010c952077a1c89ecdd71fc4d574c75a8f5617 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/ffbce350c6fd1e99116ea57383b9031717e36d3b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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