CVE-2026-98684
- Source
- https://cve.org/CVERecord?id=CVE-2026-98684
- Import Source
- https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98684.json
- JSON Data
- https://api.osv.dev/v1/vulns/CVE-2026-98684
- Downstream
- Published
- 2026-10-18T15:45:52Z
- Modified
- 2026-10-19T02:47:07Z
- Summary
- smb: client: flush and commit data before querying allocated ranges
- Details
-
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.
- Database specific
{ "cna_assigner": "Linux", "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98684.json" }- References
-
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
- https://git.kernel.org/stable/c/aa994489bd835547c191827acc460192e147032d
- https://git.kernel.org/stable/c/bf84e44ff0ed802778eafd7ecb623635379cb506
- https://git.kernel.org/stable/c/f82242fe3109a3ef72f429540b5bdde08fbfb0e4
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98684.json
- https://nvd.nist.gov/vuln/detail/CVE-2026-98684
Affected packages
Git / git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Affected ranges
- Type
- GIT
- Repo
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
- Events
-
Introduced966a3cb7c7db786452a87afdc3b48858fc4d4d6bFixedf82242fe3109a3ef72f429540b5bdde08fbfb0e4Fixedbf84e44ff0ed802778eafd7ecb623635379cb506Fixedaa994489bd835547c191827acc460192e147032d
- Type
- GIT
- Repo
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
- Events
-
Introduced5.10.50Fixed5.11
- Type
- GIT
- Repo
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
- Events
-
Introduced5.12.17Fixed5.13
- Type
- GIT
- Repo
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
- Events
-
Introduced5.13.2Fixed5.14
- Type
- GIT
- Repo
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
- Events
-
Introducedc406bb9ece6ef63721daab106f132ff4b4234e81
- Type
- GIT
- Repo
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
- Events
-
Introduced2f9f4a2d0e6fcf0673ed51195e06e47abe966900
- Type
- GIT
- Repo
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
- Events
-
Introduced5e397c943424de94879830e72c95f2679e297a76