cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0 (CVE-2026-89640) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-89640

cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0

Answer in brief

CVE-2026-89640 records a Unknown severity vulnerability in cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 11, 2026Updated Sep 11, 2026Source checked Sep 11, 2026First seen by HOL Sep 11, 2026Material review Sep 11, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Linux/Linuxgeneric	>=04b38d601239b4d9be641b412cf4b7456a041c67 <b098f5e5858797827666e6cd73033f52fc39b5f6 \|\| >=04b38d601239b4d9be641b412cf4b7456a041c67 <c2a0dcb5a7a1516aa6eb6d5cedca6a8e76527028 \|\| >=04b38d601239b4d9be641b412cf4b7456a041c67 <b057ca17b656345d04669cb87f2aff9b31d873db \|\| >=04b38d601239b4d9be641b412cf4b7456a041c67 <6c322f5cf7476ded7a9a20f7be72462065a03c68	b098f5e5858797827666e6cd73033f52fc39b5f6, c2a0dcb5a7a1516aa6eb6d5cedca6a8e76527028, b057ca17b656345d04669cb87f2aff9b31d873db, 6c322f5cf7476ded7a9a20f7be72462065a03c68
Linux/Linuxgeneric	4.5	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux.
Review the reported fix. Update Linux/Linux to b098f5e5858797827666e6cd73033f52fc39b5f6 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 11, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 11, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 11, 2026

Sources and claim methodology

Upstream source 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().

Quoted source text, attributed separately from HOL analysis.