CVE-2026-98684 - Vulnerability Details

Vendors	Products
Linux Subscribe	Linux Kernel Subscribe

Link	Providers
https://git.kernel.org/stable/c/aa994489bd835547c191827acc460192e147032d
https://git.kernel.org/stable/c/bf84e44ff0ed802778eafd7ecb623635379cb506
https://git.kernel.org/stable/c/f82242fe3109a3ef72f429540b5bdde08fbfb0e4

Type	Values Removed	Values Added
Description		In the Linux kernel, the following vulnerability has been resolved: smb: client: flush and commit data before querying allocated ranges The mode 0 / FALLOC_FL_KEEP_SIZE fallocate emulation for small interior ranges in smb3_simple_fallocate_range() issues FSCTL_QUERY_ALLOCATED_RANGES and zero-fills any sub-range the server reports as an unallocated hole, to force block allocation without changing file contents. This is unsafe against Windows servers. Per the Win32 documentation, FSCTL_QUERY_ALLOCATED_RANGES only reports ranges that may contain nonzero data and is explicitly not coherent with recently written data: "a call to FSCTL_QUERY_ALLOCATED_RANGES [after writing to a network file] would not necessarily return a correct list of allocated regions. To ensure coherency [...] flush the data to the file" fsx (generic/363) reproduces the resulting corruption against Windows Server 2022: a range is written, an uncached read returns the data, yet the next FSCTL_QUERY_ALLOCATED_RANGES on that range reports it as a whole hole, so the emulation overwrites live data with zeroes. A network trace confirmed the WRITE, the READ returning data and the query returning an empty range list within microseconds. Samba does not exhibit this; its query is coherent with the written data. Write back the dirty pages, drain any outstanding I/O and issue an SMB2 FLUSH to force the server to commit the data before querying the allocated ranges, so the query reflects the data actually present. With this, generic/363 passes against both Windows Server 2022 and Samba over 100000 fsx operations.
Title		smb: client: flush and commit data before querying allocated ranges
First Time appeared		Linux Linux linux Kernel
CPEs		cpe:2.3:o:linux:linux_kernel::::::::
Vendors & Products		Linux Linux linux Kernel
References		https://git.kernel.org/stable/c/aa994489bd835547c191827acc460192e147032d https://git.kernel.org/stable/c/bf84e44ff0ed802778eafd7ecb623635379cb506 https://git.kernel.org/stable/c/f82242fe3109a3ef72f429540b5bdde08fbfb0e4

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-98684", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-25T10:25:14.364Z", "datePublished": "2026-10-18T15:45:52.828Z", "dateUpdated": "2026-10-18T15:45:52.828Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-18T15:45:52.828Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: flush and commit data before querying allocated ranges\n\nThe mode 0 / FALLOC_FL_KEEP_SIZE fallocate emulation for small interior\nranges in smb3_simple_fallocate_range() issues\nFSCTL_QUERY_ALLOCATED_RANGES and zero-fills any sub-range the server\nreports as an unallocated hole, to force block allocation without\nchanging file contents.\n\nThis is unsafe against Windows servers. Per the Win32 documentation,\nFSCTL_QUERY_ALLOCATED_RANGES only reports ranges that *may* contain\nnonzero data and is explicitly not coherent with recently written data:\n\n \"a call to FSCTL_QUERY_ALLOCATED_RANGES [after writing to a network\n file] would not necessarily return a correct list of allocated\n regions. To ensure coherency [...] flush the data to the file\"\n\nfsx (generic/363) reproduces the resulting corruption against Windows\nServer 2022: a range is written, an uncached read returns the data, yet\nthe next FSCTL_QUERY_ALLOCATED_RANGES on that range reports it as a whole\nhole, so the emulation overwrites live data with zeroes. A network trace\nconfirmed the WRITE, the READ returning data and the query returning an\nempty range list within microseconds. Samba does not exhibit this; its\nquery is coherent with the written data.\n\nWrite back the dirty pages, drain any outstanding I/O and issue an SMB2\nFLUSH to force the server to commit the data before querying the\nallocated ranges, so the query reflects the data actually present.\n\nWith this, generic/363 passes against both Windows Server 2022 and Samba\nover 100000 fsx operations."}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/smb/client/smb2ops.c"], "versions": [{"version": "966a3cb7c7db786452a87afdc3b48858fc4d4d6b", "lessThan": "f82242fe3109a3ef72f429540b5bdde08fbfb0e4", "status": "affected", "versionType": "git"}, {"version": "966a3cb7c7db786452a87afdc3b48858fc4d4d6b", "lessThan": "bf84e44ff0ed802778eafd7ecb623635379cb506", "status": "affected", "versionType": "git"}, {"version": "966a3cb7c7db786452a87afdc3b48858fc4d4d6b", "lessThan": "aa994489bd835547c191827acc460192e147032d", "status": "affected", "versionType": "git"}, {"version": "c406bb9ece6ef63721daab106f132ff4b4234e81", "status": "affected", "versionType": "git"}, {"version": "2f9f4a2d0e6fcf0673ed51195e06e47abe966900", "status": "affected", "versionType": "git"}, {"version": "5e397c943424de94879830e72c95f2679e297a76", "status": "affected", "versionType": "git"}, {"version": "5.10.50", "lessThan": "5.11", "status": "affected", "versionType": "semver"}, {"version": "5.12.17", "lessThan": "5.13", "status": "affected", "versionType": "semver"}, {"version": "5.13.2", "lessThan": "5.14", "status": "affected", "versionType": "semver"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/smb/client/smb2ops.c"], "versions": [{"version": "5.14", "status": "affected"}, {"version": "0", "lessThan": "5.14", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.56", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.2.10", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.3-rc6", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.14", "versionEndExcluding": "6.18.56"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.14", "versionEndExcluding": "7.2.10"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.14", "versionEndExcluding": "7.3-rc6"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.10.50"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.12.17"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.13.2"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/f82242fe3109a3ef72f429540b5bdde08fbfb0e4"}, {"url": "https://git.kernel.org/stable/c/bf84e44ff0ed802778eafd7ecb623635379cb506"}, {"url": "https://git.kernel.org/stable/c/aa994489bd835547c191827acc460192e147032d"}], "title": "smb: client: flush and commit data before querying allocated ranges", "x_generator": {"engine": "bippy-1.2.0"}}}}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["fs/smb/client/smb2ops.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "f82242fe3109a3ef72f429540b5bdde08fbfb0e4", "status": "affected", "version": "966a3cb7c7db786452a87afdc3b48858fc4d4d6b", "versionType": "git"}, {"lessThan": "bf84e44ff0ed802778eafd7ecb623635379cb506", "status": "affected", "version": "966a3cb7c7db786452a87afdc3b48858fc4d4d6b", "versionType": "git"}, {"lessThan": "aa994489bd835547c191827acc460192e147032d", "status": "affected", "version": "966a3cb7c7db786452a87afdc3b48858fc4d4d6b", "versionType": "git"}, {"status": "affected", "version": "c406bb9ece6ef63721daab106f132ff4b4234e81", "versionType": "git"}, {"status": "affected", "version": "2f9f4a2d0e6fcf0673ed51195e06e47abe966900", "versionType": "git"}, {"status": "affected", "version": "5e397c943424de94879830e72c95f2679e297a76", "versionType": "git"}, {"lessThan": "5.11", "status": "affected", "version": "5.10.50", "versionType": "semver"}, {"lessThan": "5.13", "status": "affected", "version": "5.12.17", "versionType": "semver"}, {"lessThan": "5.14", "status": "affected", "version": "5.13.2", "versionType": "semver"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["fs/smb/client/smb2ops.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "5.14"}, {"lessThan": "5.14", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "6.18.*", "status": "unaffected", "version": "6.18.56", "versionType": "semver"}, {"lessThanOrEqual": "7.2.*", "status": "unaffected", "version": "7.2.10", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "7.3-rc6", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: flush and commit data before querying allocated ranges\n\nThe mode 0 / FALLOC_FL_KEEP_SIZE fallocate emulation for small interior\nranges in smb3_simple_fallocate_range() issues\nFSCTL_QUERY_ALLOCATED_RANGES and zero-fills any sub-range the server\nreports as an unallocated hole, to force block allocation without\nchanging file contents.\n\nThis is unsafe against Windows servers. Per the Win32 documentation,\nFSCTL_QUERY_ALLOCATED_RANGES only reports ranges that *may* contain\nnonzero data and is explicitly not coherent with recently written data:\n\n \"a call to FSCTL_QUERY_ALLOCATED_RANGES [after writing to a network\n file] would not necessarily return a correct list of allocated\n regions. To ensure coherency [...] flush the data to the file\"\n\nfsx (generic/363) reproduces the resulting corruption against Windows\nServer 2022: a range is written, an uncached read returns the data, yet\nthe next FSCTL_QUERY_ALLOCATED_RANGES on that range reports it as a whole\nhole, so the emulation overwrites live data with zeroes. A network trace\nconfirmed the WRITE, the READ returning data and the query returning an\nempty range list within microseconds. Samba does not exhibit this; its\nquery is coherent with the written data.\n\nWrite back the dirty pages, drain any outstanding I/O and issue an SMB2\nFLUSH to force the server to commit the data before querying the\nallocated ranges, so the query reflects the data actually present.\n\nWith this, generic/363 passes against both Windows Server 2022 and Samba\nover 100000 fsx operations."}], "id": "CVE-2026-98684", "lastModified": "2026-10-18T16:17:21.770", "metrics": {}, "published": "2026-10-18T16:17:21.770", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/aa994489bd835547c191827acc460192e147032d"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/bf84e44ff0ed802778eafd7ecb623635379cb506"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/f82242fe3109a3ef72f429540b5bdde08fbfb0e4"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Received"}

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