CVE-2026-68388smb/client: handle overlapping allocated ranges in fallocate
Updated under an hour ago ()
Does this affect you?
It affects Linux. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
Do this next
Free account, 1 product
In the Linux kernel, the following vulnerability has been resolved: smb/client: handle overlapping allocated ranges in fallocate smb3_simple_fallocate_range() can skip holes when an allocated range returned by the server starts before the current fallocate offset. The skipped hole is not zero-filled, but fallocate still returns success. A later write to that hole may therefore fail with ENOSPC. The function queries allocated ranges so that it can preserve existing contents and write zeroes only into holes. However, the server may return a range that starts before the current fallocate offset. For example, assume the fallocate request is [100, 400) and the only allocated range returned by the server is [0, 200): Request: [100, 400) Server range: [ 0, 200) allocated Correct: [100, 200) allocated data, skip [200, 400) hole, zero-fill Current: [100, 300) skipped [300, 400) zero-filled afterwards The current code adds the full server range length, 200, to the current offset 100 and moves to 300. As a result, the hole in [200, 300) is skipped without being zero-filled. Fix this by advancing only over the part of the allocated range that overlaps the current fallocate offset. Ignore ranges that end before the current offset and reject ranges whose end offset overflows. This also prevents a malformed range length from causing an out-of-bounds zero-buffer read.
- CVSS
- 9.8 CRITICAL (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- 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 16, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Linux Linux linux:linux (from the name) | from c406bb9ece6ef63721daab106f132ff4b4234e81 before aeb58a4eb39a7ff4d7782b4f4ada0fda5e0675d2; from 966a3cb7c7db786452a87afdc3b48858fc4d4d6b before 01719883235507b1585e4c51e320d9a7113dc698; from 966a3cb7c7db786452a87afdc3b48858fc4d4d6b before f47c7277c03a636fcc3a57969f2dc09567b3c050; from 966a3cb7c7db786452a87afdc3b48858fc4d4d6b before 437637f5ff3f573b2edf8571de91fb00a21eb4e6; 966a3cb7c7db786452a87afdc3b48858fc4d4d6b builds before 377fe3e583e46369ee1004d5cfe12271d6589a68; 966a3cb7c7db786452a87afdc3b48858fc4d4d6b builds before 7e08ab7a061b17ac1989a225c6afb53f44a86808; from 966a3cb7c7db786452a87afdc3b48858fc4d4d6b before a4a09e5142835633fffbde68bd0a039ba4d4bf97; from 966a3cb7c7db786452a87afdc3b48858fc4d4d6b before b09ae45d85dc816987a71db9eebc54b0ae288e94; and 5 more ranges | CNA record |
References
- https://git.kernel.org/stable/c/aeb58a4eb39a7ff4d7782b4f4ada0fda5e0675d2
- https://git.kernel.org/stable/c/01719883235507b1585e4c51e320d9a7113dc698
- https://git.kernel.org/stable/c/f47c7277c03a636fcc3a57969f2dc09567b3c050
- https://git.kernel.org/stable/c/437637f5ff3f573b2edf8571de91fb00a21eb4e6
- https://git.kernel.org/stable/c/377fe3e583e46369ee1004d5cfe12271d6589a68
- https://git.kernel.org/stable/c/7e08ab7a061b17ac1989a225c6afb53f44a86808
- https://git.kernel.org/stable/c/a4a09e5142835633fffbde68bd0a039ba4d4bf97
- https://git.kernel.org/stable/c/b09ae45d85dc816987a71db9eebc54b0ae288e94
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.