CVE-2026-68388 is a vulnerability in Linux Kernel
Published on August 10, 2026
smb/client: handle overlapping allocated ranges in fallocate
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.
Products Associated with CVE-2026-68388
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Affected Versions
Linux:- Version 966a3cb7c7db786452a87afdc3b48858fc4d4d6b and below 437637f5ff3f573b2edf8571de91fb00a21eb4e6 is affected.
- Version 966a3cb7c7db786452a87afdc3b48858fc4d4d6b and below 377fe3e583e46369ee1004d5cfe12271d6589a68 is affected.
- Version 966a3cb7c7db786452a87afdc3b48858fc4d4d6b and below 7e08ab7a061b17ac1989a225c6afb53f44a86808 is affected.
- Version 966a3cb7c7db786452a87afdc3b48858fc4d4d6b and below a4a09e5142835633fffbde68bd0a039ba4d4bf97 is affected.
- Version 966a3cb7c7db786452a87afdc3b48858fc4d4d6b and below b09ae45d85dc816987a71db9eebc54b0ae288e94 is affected.
- Version c406bb9ece6ef63721daab106f132ff4b4234e81 is affected.
- Version 2f9f4a2d0e6fcf0673ed51195e06e47abe966900 is affected.
- Version 5e397c943424de94879830e72c95f2679e297a76 is affected.
- Version 5.10.50 and below 5.11 is affected.
- Version 5.12.17 and below 5.13 is affected.
- Version 5.13.2 and below 5.14 is affected.
- Version 5.14 is affected.
- Before 5.14 is unaffected.
- Version 6.6.148, <= 6.6.* is unaffected.
- Version 6.12.101, <= 6.12.* is unaffected.
- Version 6.18.42, <= 6.18.* is unaffected.
- Version 7.1.6, <= 7.1.* is unaffected.
- Version 7.2-rc4, <= * is unaffected.