ksmbd: OOB read regression in smb_check_perm_dacl() ACE-walk loops

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-63909
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-19 16:17:08 UTC
Updated2026-07-20 15:16:54 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: ksmbd: OOB read regression in smb_check_perm_dacl() ACE-walk loops Commit d07b26f39246 ("ksmbd: require minimum ACE size in smb_check_perm_dacl()") introduced a transposed bounds check: if (offsetof(struct smb_ace, sid) + aces_size < CIFS_SID_BASE_SIZE) Since offsetof(..sid) is 8 and CIFS_SID_BASE_SIZE is 8, this evaluates to `aces_size < 0`. Because `aces_size` is always non-negative, this check becomes dead code and never breaks the loop. Worse, that commit removed the old 4-byte guard, meaning the loop now reads `ace->size` (offset 2) even when `aces_size` is 0-3 bytes. This re-opens a 2-byte heap out-of-bounds (OOB) read past the pntsd allocation during subsequent SMB2_CREATE operations. Fix this by properly transposing the comparison to require at least 16 bytes (8-byte offset + 8-byte SID base), matching the correct form used in smb_inherit_dacl().

Risk And Classification

Primary CVSS: v3.1 8.1 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

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

EPSS: 0.002150000 probability, percentile 0.119430000 (date 2026-07-20)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary8.1HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
3.1CNADECLARED8.1HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

CVSS v3.1 Breakdown

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

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 282cbbb476b9f35793452bc461934af4c7eca169 5500ba1d410aed1eded3eb04a76b10cfb4409334 git Not specified
CNA Linux Linux affected f20adc4ef7428bc485ee83fd1a592252fb87718b f6324b4240cf0b26a84c33f68a1222d727ff4af2 git Not specified
CNA Linux Linux affected 325d4ac11f526cb8964cff14548ccf02d8c756d8 0fe08c5776a798f46df1fd74b331be26bdd644d6 git Not specified
CNA Linux Linux affected 95e5aa3c3261da8c95b27d7aecf8ee39b9f86a4c d333af32e4451285e427f2d9c29de3a39f6f6d48 git Not specified
CNA Linux Linux affected 90089584b2e25c4510b7b987387b4405f0673ece 94215d55b09445993929f4fc966061d61de74929 git Not specified
CNA Linux Linux affected 151b1799861fde38087c08f613abc2843ef597b0 4f7c131d2bdd7cd64b96f60d10be5ea72253f520 git Not specified
CNA Linux Linux affected d07b26f39246a82399661936dd0c853983cfade7 0e60dafe97eca61721f3db456f97d97a80c6c8ae git Not specified
CNA Linux Linux affected 6.6.140 6.6.143 semver Not specified
CNA Linux Linux affected 6.12.84 6.12.93 semver Not specified
CNA Linux Linux affected 6.18.25 6.18.35 semver Not specified
CNA Linux Linux affected 7.0.2 7.0.12 semver Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/0fe08c5776a798f46df1fd74b331be26bdd644d6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/94215d55b09445993929f4fc966061d61de74929 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/4f7c131d2bdd7cd64b96f60d10be5ea72253f520 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f6324b4240cf0b26a84c33f68a1222d727ff4af2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0e60dafe97eca61721f3db456f97d97a80c6c8ae 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/5500ba1d410aed1eded3eb04a76b10cfb4409334 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d333af32e4451285e427f2d9c29de3a39f6f6d48 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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