CVE-2026-89640
cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0
Description
In the Linux kernel, the following vulnerability has been resolved: cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0 With len == 0 (clone to EOF), the effective length is computed as: len = src_inode->i_size - off; If off > i_size, this is a negative loff_t, corrupting the ByteCount in the FSCTL_DUPLICATE_EXTENTS_TO_FILE request and inverting the range in filemap_write_and_wait_range(). The existing off >= i_size check fires only after the ioctl has already been sent. Snapshot i_size_read() once for both the bounds check and the length calculation, eliminating the TOCTOU and 32-bit torn-read risk. Reject off > src_size with -EINVAL. Treat off == src_size as a no-op, consistent with __generic_remap_file_range_prep().
INFO
Published Date :
Sept. 11, 2026, 8:19 p.m.
Last Modified :
Sept. 14, 2026, 1:19 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 |
Solution
- Apply the Linux kernel patch for cifs_remap_file_range().
- Snapshot i_size for bounds check and length calculation.
- Reject offsets greater than source size.
- Treat equal offsets as no-operation.
References to Advisories, Solutions, and Tools
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CVE-2026-89640.
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associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
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weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
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CVE-2026-89640 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-89640 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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CVE Modified by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Sep. 14, 2026
Action Type Old Value New Value Added Affected Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/89xxx/CVE-2026-89640.json">CVE-2026-89640</a> Added Reference https://git.kernel.org/stable/c/7f62817fe049b0f3652518c1ba72631ec1e0a322 Added Reference https://git.kernel.org/stable/c/f3d1ae1e6bc4a9f559185b6e7bd2b6375ec2fdd4 -
CVE Modified by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Sep. 13, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H -
New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Sep. 11, 2026
Action Type Old Value New Value Added Description In the Linux kernel, the following vulnerability has been resolved: cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0 With len == 0 (clone to EOF), the effective length is computed as: len = src_inode->i_size - off; If off > i_size, this is a negative loff_t, corrupting the ByteCount in the FSCTL_DUPLICATE_EXTENTS_TO_FILE request and inverting the range in filemap_write_and_wait_range(). The existing off >= i_size check fires only after the ioctl has already been sent. Snapshot i_size_read() once for both the bounds check and the length calculation, eliminating the TOCTOU and 32-bit torn-read risk. Reject off > src_size with -EINVAL. Treat off == src_size as a no-op, consistent with __generic_remap_file_range_prep(). Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/89xxx/CVE-2026-89640.json">CVE-2026-89640</a> Added Reference https://git.kernel.org/stable/c/6c322f5cf7476ded7a9a20f7be72462065a03c68 Added Reference https://git.kernel.org/stable/c/b057ca17b656345d04669cb87f2aff9b31d873db Added Reference https://git.kernel.org/stable/c/b098f5e5858797827666e6cd73033f52fc39b5f6 Added Reference https://git.kernel.org/stable/c/c2a0dcb5a7a1516aa6eb6d5cedca6a8e76527028