CVE-2026-68388
CriticalCVSS 9.8Exploitation Probability (EPSS)
Low risk38th percentile - higher than 38% of all known CVEs
Summary
In the Linux kernel, the SMB client has a vulnerability in the fallocate function that can skip holes when the server returns an allocated range starting before the current offset. This can cause later writes to the skipped area to fail with ENOSPC.
Risk Assessment
This could lead to data inconsistency and write errors on SMB shares, potentially disrupting applications using those resources.
Recommendation
Apply a Linux kernel update containing the fix that correctly handles overlapping allocated ranges in fallocate.
Other vulnerabilities in Linux kernel
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- CVE-2026-100072Unknown
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- CVE-2026-100071Unknown
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Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS