CVE-2026-98684smb: client: flush and commit data before querying allocated ranges
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- Not yet scored
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Received
- Record last updated
- Oct 18, 2026
- First seen by InfoSec Signals
- Oct 18, 2026
Affected products
Linux Linux linux:linux (from the name) | from 966a3cb7c7db786452a87afdc3b48858fc4d4d6b before f82242fe3109a3ef72f429540b5bdde08fbfb0e4; from 966a3cb7c7db786452a87afdc3b48858fc4d4d6b before bf84e44ff0ed802778eafd7ecb623635379cb506; from 966a3cb7c7db786452a87afdc3b48858fc4d4d6b before aa994489bd835547c191827acc460192e147032d; c406bb9ece6ef63721daab106f132ff4b4234e81; 2f9f4a2d0e6fcf0673ed51195e06e47abe966900; 5e397c943424de94879830e72c95f2679e297a76; from 5.10.50 before 5.11; from 5.12.17 before 5.13; and 1 more ranges | CNA record |
References
- https://git.kernel.org/stable/c/f82242fe3109a3ef72f429540b5bdde08fbfb0e4
- https://git.kernel.org/stable/c/bf84e44ff0ed802778eafd7ecb623635379cb506
- https://git.kernel.org/stable/c/aa994489bd835547c191827acc460192e147032d
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.