---
cve: "CVE-2026-89640"
severity: "HIGH"
cvss: 7.1
epss: "13%"
vendor: "Linux"
kev: false
exploited: false
published: "2026-09-11 20:19:49"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-17T16:01:31+02:00"
---

# CVE-2026-89640

> 7.1 HIGH

## Beschreibung

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().

## CVSS-Vektor

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

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Lokal | good |
| AC Komplexität | Gering | bad |
| PR Privilegien | Gering | warn |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Keine | good |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Hoch | bad |

## Patch verfügbar (OSV)

- Kernel ≥ 6.1.188
- Kernel ≥ 6.6.157
- Kernel ≥ 6.12.109
- Kernel ≥ 6.18.50
- Kernel ≥ 7.2.4

## Referenzen

- <https://git.kernel.org/stable/c/f3d1ae1e6bc4a9f559185b6e7bd2b6375ec2fdd4>
- <https://git.kernel.org/stable/c/7f62817fe049b0f3652518c1ba72631ec1e0a322>
- <https://git.kernel.org/stable/c/b098f5e5858797827666e6cd73033f52fc39b5f6>
- <https://git.kernel.org/stable/c/c2a0dcb5a7a1516aa6eb6d5cedca6a8e76527028>
- <https://git.kernel.org/stable/c/b057ca17b656345d04669cb87f2aff9b31d873db>
- <https://git.kernel.org/stable/c/6c322f5cf7476ded7a9a20f7be72462065a03c68>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-89640) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_