CVE-2026-64398 (GCVE-0-2026-64398)
Vulnerability from cvelistv5 – Published: 2026-07-25 08:50 – Updated: 2026-07-27 05:00
VLAI
EPSS
VEX
Title
ksmbd: add a permission check for FSCTL_SET_ZERO_DATA
Summary
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: add a permission check for FSCTL_SET_ZERO_DATA
FSCTL_SET_ZERO_DATA in smb2_ioctl() destroys file data via
ksmbd_vfs_zero_data() -> vfs_fallocate(PUNCH_HOLE/ZERO_RANGE) after
checking only the share-level KSMBD_TREE_CONN_FLAG_WRITABLE, with no
per-handle access check. A handle opened with only FILE_WRITE_ATTRIBUTES
still yields an FMODE_WRITE filp (FILE_WRITE_ATTRIBUTES is part of
FILE_WRITE_DESIRE_ACCESS_LE, so smb2_create_open_flags() opens it
O_WRONLY), so the vfs_fallocate FMODE_WRITE check does not stop it; only
the missing fp->daccess gate would. Reproduced on mainline 7.1-rc7 with
KASAN by an authenticated SMB client: a FILE_WRITE_ATTRIBUTES-only handle
zeroed 4096 bytes of file data it had no FILE_WRITE_DATA right to
(6/6; a FILE_READ_DATA-only handle was correctly denied).
This is the unfixed sibling of commit cc57232cae23 ("ksmbd: fix FSCTL
permission bypass by adding a permission check for FSCTL_SET_SPARSE").
Because SET_ZERO_DATA writes data (not an attribute), require
FILE_WRITE_DATA.
Severity
8.1 (High)
Assigner
References
6 references
Impacted products
2 products
| Vendor | Product | Version | |
|---|---|---|---|
| Linux | Linux |
Affected:
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 25377f369688dd0bd814dc8965ed26d44238ecaa
(git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 3072d82461f498c85daea8766e9d8bfbada31605 (git) Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < ca53bb17f4e8232cfaece3953d3cef62c559b039 (git) Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 57f2042fd87d7ce8fc3ac8b6c176e554df68b1a7 (git) Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < deffa929086d7902e30918adf3dd27ccfe9c08b1 (git) Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 3320ba068198adc144c89d6661b805acce01735b (git) |
|
| Linux | Linux |
Affected:
5.15
Unaffected: 0 , < 5.15 (semver) Unaffected: 6.1.178 , ≤ 6.1.* (semver) Unaffected: 6.6.145 , ≤ 6.6.* (semver) Unaffected: 6.12.96 , ≤ 6.12.* (semver) Unaffected: 6.18.39 , ≤ 6.18.* (semver) Unaffected: 7.1.4 , ≤ 7.1.* (semver) Unaffected: 7.2-rc1 , ≤ * (original_commit_for_fix) |
{
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"programFiles": [
"fs/smb/server/smb2pdu.c"
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],
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"vendor": "Linux",
"versions": [
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},
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"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
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"status": "unaffected",
"version": "6.1.178",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.145",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.96",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.39",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.4",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2-rc1",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
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"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: add a permission check for FSCTL_SET_ZERO_DATA\n\nFSCTL_SET_ZERO_DATA in smb2_ioctl() destroys file data via\nksmbd_vfs_zero_data() -\u003e vfs_fallocate(PUNCH_HOLE/ZERO_RANGE) after\nchecking only the share-level KSMBD_TREE_CONN_FLAG_WRITABLE, with no\nper-handle access check. A handle opened with only FILE_WRITE_ATTRIBUTES\nstill yields an FMODE_WRITE filp (FILE_WRITE_ATTRIBUTES is part of\nFILE_WRITE_DESIRE_ACCESS_LE, so smb2_create_open_flags() opens it\nO_WRONLY), so the vfs_fallocate FMODE_WRITE check does not stop it; only\nthe missing fp-\u003edaccess gate would. Reproduced on mainline 7.1-rc7 with\nKASAN by an authenticated SMB client: a FILE_WRITE_ATTRIBUTES-only handle\nzeroed 4096 bytes of file data it had no FILE_WRITE_DATA right to\n(6/6; a FILE_READ_DATA-only handle was correctly denied).\n\nThis is the unfixed sibling of commit cc57232cae23 (\"ksmbd: fix FSCTL\npermission bypass by adding a permission check for FSCTL_SET_SPARSE\").\nBecause SET_ZERO_DATA writes data (not an attribute), require\nFILE_WRITE_DATA."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 8.1,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H",
"version": "3.1"
}
}
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"providerMetadata": {
"dateUpdated": "2026-07-27T05:00:29.523Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
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"url": "https://git.kernel.org/stable/c/25377f369688dd0bd814dc8965ed26d44238ecaa"
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{
"url": "https://git.kernel.org/stable/c/3072d82461f498c85daea8766e9d8bfbada31605"
},
{
"url": "https://git.kernel.org/stable/c/ca53bb17f4e8232cfaece3953d3cef62c559b039"
},
{
"url": "https://git.kernel.org/stable/c/57f2042fd87d7ce8fc3ac8b6c176e554df68b1a7"
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{
"url": "https://git.kernel.org/stable/c/deffa929086d7902e30918adf3dd27ccfe9c08b1"
},
{
"url": "https://git.kernel.org/stable/c/3320ba068198adc144c89d6661b805acce01735b"
}
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"title": "ksmbd: add a permission check for FSCTL_SET_ZERO_DATA",
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"cveId": "CVE-2026-64398",
"datePublished": "2026-07-25T08:50:42.221Z",
"dateReserved": "2026-07-19T15:36:31.785Z",
"dateUpdated": "2026-07-27T05:00:29.523Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-64398",
"date": "2026-07-26",
"epss": "0.00181",
"percentile": "0.07958"
},
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"current_release_date": "2026-07-26T01:05:02.000Z",
"cve": "CVE-2026-64398",
"id": "msrc_CVE-2026-64398",
"initial_release_date": "2026-07-26T01:05:02.000Z",
"product_status:under_investigation": "1",
"source": "Microsoft CSAF VEX",
"status": "final",
"title": "ksmbd: add a permission check for FSCTL_SET_ZERO_DATA",
"url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-64398.json",
"version": "1"
},
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Reproduced on mainline 7.1-rc7 with\\nKASAN by an authenticated SMB client: a FILE_WRITE_ATTRIBUTES-only handle\\nzeroed 4096 bytes of file data it had no FILE_WRITE_DATA right to\\n(6/6; a FILE_READ_DATA-only handle was correctly denied).\\n\\nThis is the unfixed sibling of commit cc57232cae23 (\\\"ksmbd: fix FSCTL\\npermission bypass by adding a permission check for FSCTL_SET_SPARSE\\\").\\nBecause SET_ZERO_DATA writes data (not an attribute), require\\nFILE_WRITE_DATA.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/smb/server/smb2pdu.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9\",\"lessThan\":\"25377f369688dd0bd814dc8965ed26d44238ecaa\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9\",\"lessThan\":\"3072d82461f498c85daea8766e9d8bfbada31605\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9\",\"lessThan\":\"ca53bb17f4e8232cfaece3953d3cef62c559b039\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9\",\"lessThan\":\"57f2042fd87d7ce8fc3ac8b6c176e554df68b1a7\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9\",\"lessThan\":\"deffa929086d7902e30918adf3dd27ccfe9c08b1\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9\",\"lessThan\":\"3320ba068198adc144c89d6661b805acce01735b\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/smb/server/smb2pdu.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"5.15\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"5.15\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.1.178\",\"lessThanOrEqual\":\"6.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.145\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.96\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.39\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.4\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2-rc1\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"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:N/I:H/A:H\",\"baseScore\":8.1,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":2.8,\"impactScore\":5.2}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/25377f369688dd0bd814dc8965ed26d44238ecaa\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/3072d82461f498c85daea8766e9d8bfbada31605\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/3320ba068198adc144c89d6661b805acce01735b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/57f2042fd87d7ce8fc3ac8b6c176e554df68b1a7\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/ca53bb17f4e8232cfaece3953d3cef62c559b039\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/deffa929086d7902e30918adf3dd27ccfe9c08b1\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
"suse_vex": {
"aggregate_severity": "not set",
"current_release_date": "2026-07-25T16:00:05Z",
"cve": "CVE-2026-64398",
"id": "CVE-2026-64398",
"initial_release_date": "2026-07-25T16:00:05Z",
"source": "SUSE CSAF VEX",
"status": "interim",
"title": "SUSE CVE CVE-2026-64398",
"url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-64398.json",
"version": "2"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
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