---
cve: "CVE-2026-63940"
severity: "CRITICAL"
cvss: 9.3
epss: "0.2%"
vendor: "Linux"
kev: false
exploited: false
published: "2026-07-19 14:55:36"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-10-23T10:31:59+02:00"
---

# CVE-2026-63940

> 9.3 CRITICAL

## Beschreibung

In the Linux kernel, the following vulnerability has been resolved:

KVM: SEV: Ignore Port I/O requests of length '0'

Explicitly ignore Port I/O requests of length '0' (or count '0'), so that
setting up the software scratch area (and other code) doesn't have to
worry about underflowing the length, and to allow for WARNing on trying
to configure the scratch area with len==0.

## CNA-Record (Kanon, cvelistV5)

- CNA: **Linux**
- State: PUBLISHED
- Stand: 2026-10-21 12:42:44
- CNA-CVSS: **9.3** (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H`)

## CISA-Anreicherung (vulnrichment/ADP)

- CISA-SSVC (Coordinator, v2.0.3):
  - Exploitation: **none**
  - Automatable: **no**
  - Technical Impact: **total**

## CVSS-Vektor

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

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

## Schwachstellen-Klasse

- **CWE-190** — Integer Overflow or Wraparound
  The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

## Angriffsmuster (CAPEC)

- [CAPEC-92 — Forced Integer Overflow](https://capec.mitre.org/data/definitions/92.html) _(Severity: High)_

## Patch verfügbar (OSV)

- Kernel ≥ 6.6.160
- Kernel ≥ 6.12.95
- Kernel ≥ 6.18.35
- Kernel ≥ 7.0.12

## BSI-Hinweise (deutsch)

- [Linux Kernel: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff](https://wid.cert-bund.de/portal/wid/sicherheitshinweis/WID-SEC-W-2026-2403) — _BSI-Einstufung: mittel_
  Ein Angreifer kann mehrere Schwachstellen im Linux Kernel ausnutzen, um einen nicht näher spezifizierten Angriff durchzuführen, möglicherweise Sicherheitsmaßnahmen zu umgehen, einen Denial-of-Service-Zustand herbeizuführen oder vertrauliche Informationen offenzulegen.

## Referenzen

- <https://git.kernel.org/stable/c/bbd3a27e4f99fdcad82d12d79c04a95dff1ff70b>
- <https://git.kernel.org/stable/c/3b6035bc6bff20e89752ce4358bc4c9a9d5883f2>
- <https://git.kernel.org/stable/c/2254972d4d69e279ba4e87bf0968eb08ad0d3c92>
- <https://git.kernel.org/stable/c/c30cde934c7813b4e3069765dac64ce3d31e34f2>
- <https://git.kernel.org/stable/c/3988bd2723de407ae90fa7a6f6029b4e60238c58>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/sicherheitsluecken/cve-2026-63940/) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_