---
title: "CVE-2026-89640: Linux Kernel - Data Tampering & Denial of Service"
description: "Linux kernel contains a vulnerability in cifs_remap_file_range() caused by loff_t underflow when len is 0, letting attackers cause file range corruption, exploit requires crafted FSCTL_DUPLICATE_EXTENTS_TO_FILE request."
url: https://panop.io/threat-heartbeat/CVE-2026-89640/
---

# CVE-2026-89640 Linux Kernel - Data Tampering & Denial of Service

Linux kernel contains a vulnerability in cifs\_remap\_file\_range() caused by loff\_t underflow when len is 0, letting attackers cause file range corruption, exploit requires crafted FSCTL\_DUPLICATE\_EXTENTS\_TO\_FILE request.

CVSS base score 7.1 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Required

EPSS

0.13% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-89640)

## Details

Type

Data Tampering

Impact

Data Tampering, Denial Of Service

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H

Published

11 September 2026

Updated

15 October 2026

## Vendor fix

Update to the latest Linux kernel version containing the fix for cifs\_remap\_file\_range() loff\_t underflow.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-89640](https://nvd.nist.gov/vuln/detail/CVE-2026-89640)
- [https://git.kernel.org/stable/c/f3d1ae1e6bc4a9f559185b6e7bd2b6375ec2fdd4](https://git.kernel.org/stable/c/f3d1ae1e6bc4a9f559185b6e7bd2b6375ec2fdd4)
- [https://git.kernel.org/stable/c/6c322f5cf7476ded7a9a20f7be72462065a03c68](https://git.kernel.org/stable/c/6c322f5cf7476ded7a9a20f7be72462065a03c68)
- [https://git.kernel.org/stable/c/b057ca17b656345d04669cb87f2aff9b31d873db](https://git.kernel.org/stable/c/b057ca17b656345d04669cb87f2aff9b31d873db)
- [https://git.kernel.org/stable/c/b098f5e5858797827666e6cd73033f52fc39b5f6](https://git.kernel.org/stable/c/b098f5e5858797827666e6cd73033f52fc39b5f6)
- [https://git.kernel.org/stable/c/c2a0dcb5a7a1516aa6eb6d5cedca6a8e76527028](https://git.kernel.org/stable/c/c2a0dcb5a7a1516aa6eb6d5cedca6a8e76527028)
- [https://git.kernel.org/stable/c/7f62817fe049b0f3652518c1ba72631ec1e0a322](https://git.kernel.org/stable/c/7f62817fe049b0f3652518c1ba72631ec1e0a322)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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