{"api_version":"1","generated_at":"2026-07-23T22:02:30+00:00","cve":"CVE-2026-63909","urls":{"html":"https://cve.report/CVE-2026-63909","api":"https://cve.report/api/cve/CVE-2026-63909.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-63909","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-63909"},"summary":{"title":"ksmbd: OOB read regression in smb_check_perm_dacl() ACE-walk loops","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: OOB read regression in smb_check_perm_dacl() ACE-walk loops\n\nCommit d07b26f39246 (\"ksmbd: require minimum ACE size in\nsmb_check_perm_dacl()\") introduced a transposed bounds check:\n\n    if (offsetof(struct smb_ace, sid) + aces_size < CIFS_SID_BASE_SIZE)\n\nSince offsetof(..sid) is 8 and CIFS_SID_BASE_SIZE is 8, this evaluates\nto `aces_size < 0`. Because `aces_size` is always non-negative, this\ncheck becomes dead code and never breaks the loop.\n\nWorse, that commit removed the old 4-byte guard, meaning the loop now\nreads `ace->size` (offset 2) even when `aces_size` is 0-3 bytes. This\nre-opens a 2-byte heap out-of-bounds (OOB) read past the pntsd allocation\nduring subsequent SMB2_CREATE operations.\n\nFix this by properly transposing the comparison to require at least\n16 bytes (8-byte offset + 8-byte SID base), matching the correct form\nused in smb_inherit_dacl().","state":"PUBLISHED","assigner":"Linux","published_at":"2026-07-19 16:17:08","updated_at":"2026-07-20 15:16:54"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"8.1","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H","baseScore":8.1,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"NONE","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"8.1","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H","data":{"baseScore":8.1,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/0fe08c5776a798f46df1fd74b331be26bdd644d6","name":"https://git.kernel.org/stable/c/0fe08c5776a798f46df1fd74b331be26bdd644d6","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/94215d55b09445993929f4fc966061d61de74929","name":"https://git.kernel.org/stable/c/94215d55b09445993929f4fc966061d61de74929","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/4f7c131d2bdd7cd64b96f60d10be5ea72253f520","name":"https://git.kernel.org/stable/c/4f7c131d2bdd7cd64b96f60d10be5ea72253f520","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/f6324b4240cf0b26a84c33f68a1222d727ff4af2","name":"https://git.kernel.org/stable/c/f6324b4240cf0b26a84c33f68a1222d727ff4af2","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/0e60dafe97eca61721f3db456f97d97a80c6c8ae","name":"https://git.kernel.org/stable/c/0e60dafe97eca61721f3db456f97d97a80c6c8ae","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/5500ba1d410aed1eded3eb04a76b10cfb4409334","name":"https://git.kernel.org/stable/c/5500ba1d410aed1eded3eb04a76b10cfb4409334","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/d333af32e4451285e427f2d9c29de3a39f6f6d48","name":"https://git.kernel.org/stable/c/d333af32e4451285e427f2d9c29de3a39f6f6d48","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-63909","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63909","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 282cbbb476b9f35793452bc461934af4c7eca169 5500ba1d410aed1eded3eb04a76b10cfb4409334 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f20adc4ef7428bc485ee83fd1a592252fb87718b f6324b4240cf0b26a84c33f68a1222d727ff4af2 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 325d4ac11f526cb8964cff14548ccf02d8c756d8 0fe08c5776a798f46df1fd74b331be26bdd644d6 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 95e5aa3c3261da8c95b27d7aecf8ee39b9f86a4c d333af32e4451285e427f2d9c29de3a39f6f6d48 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 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the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: OOB read regression in smb_check_perm_dacl() ACE-walk loops\n\nCommit d07b26f39246 (\"ksmbd: require minimum ACE size in\nsmb_check_perm_dacl()\") introduced a transposed bounds check:\n\n    if (offsetof(struct smb_ace, sid) + aces_size < CIFS_SID_BASE_SIZE)\n\nSince offsetof(..sid) is 8 and CIFS_SID_BASE_SIZE is 8, this evaluates\nto `aces_size < 0`. Because `aces_size` is always non-negative, this\ncheck becomes dead code and never breaks the loop.\n\nWorse, that commit removed the old 4-byte guard, meaning the loop now\nreads `ace->size` (offset 2) even when `aces_size` is 0-3 bytes. This\nre-opens a 2-byte heap out-of-bounds (OOB) read past the pntsd allocation\nduring subsequent SMB2_CREATE operations.\n\nFix this by properly transposing the comparison to require at least\n16 bytes (8-byte offset + 8-byte SID base), matching the correct form\nused in smb_inherit_dacl()."}],"metrics":[{"cvssV3_1":{"baseScore":8.1,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H","version":"3.1"}}],"providerMetadata":{"dateUpdated":"2026-07-20T13:41:19.196Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/5500ba1d410aed1eded3eb04a76b10cfb4409334"},{"url":"https://git.kernel.org/stable/c/f6324b4240cf0b26a84c33f68a1222d727ff4af2"},{"url":"https://git.kernel.org/stable/c/0fe08c5776a798f46df1fd74b331be26bdd644d6"},{"url":"https://git.kernel.org/stable/c/d333af32e4451285e427f2d9c29de3a39f6f6d48"},{"url":"https://git.kernel.org/stable/c/94215d55b09445993929f4fc966061d61de74929"},{"url":"https://git.kernel.org/stable/c/4f7c131d2bdd7cd64b96f60d10be5ea72253f520"},{"url":"https://git.kernel.org/stable/c/0e60dafe97eca61721f3db456f97d97a80c6c8ae"}],"title":"ksmbd: OOB read regression in smb_check_perm_dacl() ACE-walk loops","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-63909","datePublished":"2026-07-19T14:55:15.060Z","dateReserved":"2026-07-19T07:54:57.020Z","dateUpdated":"2026-07-20T13:41:19.196Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-07-19 16:17:08","lastModifiedDate":"2026-07-20 15:16:54","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H","baseScore":8.1,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"NONE","availabilityImpact":"HIGH"},"exploitabilityScore":2.8,"impactScore":5.2}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"63909","Ordinal":"1","Title":"ksmbd: OOB read regression in smb_check_perm_dacl() ACE-walk loo","CVE":"CVE-2026-63909","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"63909","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: OOB read regression in smb_check_perm_dacl() ACE-walk loops\n\nCommit d07b26f39246 (\"ksmbd: require minimum ACE size in\nsmb_check_perm_dacl()\") introduced a transposed bounds check:\n\n    if (offsetof(struct smb_ace, sid) + aces_size < CIFS_SID_BASE_SIZE)\n\nSince offsetof(..sid) is 8 and CIFS_SID_BASE_SIZE is 8, this evaluates\nto `aces_size < 0`. Because `aces_size` is always non-negative, this\ncheck becomes dead code and never breaks the loop.\n\nWorse, that commit removed the old 4-byte guard, meaning the loop now\nreads `ace->size` (offset 2) even when `aces_size` is 0-3 bytes. This\nre-opens a 2-byte heap out-of-bounds (OOB) read past the pntsd allocation\nduring subsequent SMB2_CREATE operations.\n\nFix this by properly transposing the comparison to require at least\n16 bytes (8-byte offset + 8-byte SID base), matching the correct form\nused in smb_inherit_dacl().","Type":"Description","Title":"ksmbd: OOB read regression in smb_check_perm_dacl() ACE-walk loo"}]}}}