---
cve: "CVE-2026-63984"
severity: "CRITICAL"
cvss: 9.8
epss: "0.5%"
vendor: "Linux"
kev: false
exploited: false
published: "2026-07-19 16:17:17"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-10-31T22:39:16+01:00"
---

# CVE-2026-63984

> 9.8 CRITICAL

## Beschreibung

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

ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()

ipv6_rpl_srh_decompress() computes:

    outhdr->hdrlen = (((n + 1) * sizeof(struct in6_addr)) >> 3);

hdrlen is __u8. For n >= 127 the result exceeds 255 and silently
truncates. With n=127 (cmpri=15, cmpre=15, pad=0, hdrlen=16):

    (128 * 16) >> 3 = 256, truncated to 0 as __u8

The caller in ipv6_rpl_srh_rcv() then places the compressed header
at buf + ((ohdr->hdrlen + 1)  255, which
prevents n+1 from overflowing unsigned char (the segments_left
field), but does not prevent the computed hdrlen from overflowing
__u8. n=127 passes because 128  127. This caps n at 126, giving
hdrlen = (127 * 16) >> 3 = 254, which fits in __u8. The compressed
header then lands at buf + ((254 + 1)

## CNA-Record (Kanon, cvelistV5)

- CNA: **Linux**
- State: PUBLISHED
- Stand: 2026-10-19 20:18:00
- CNA-CVSS: **9.8** (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)

## CISA-Anreicherung (vulnrichment/ADP)

- CISA-SSVC (Coordinator, v2.0.3):
  - Exploitation: **none**
  - Automatable: **yes**
  - Technical Impact: **total**

## CVSS-Vektor

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

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| 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 ≥ 5.10.259
- Kernel ≥ 5.15.210
- Kernel ≥ 6.1.176
- Kernel ≥ 6.6.143
- Kernel ≥ 6.12.93
- 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/75b3680047bf09af8e7e471a7a6ddf2ce5847f56>
- <https://git.kernel.org/stable/c/fd238c51b0fa5390cceca9f1ac5a9ffda8063eed>
- <https://git.kernel.org/stable/c/3618b34942b76471d044369bfd30d58c39068bf1>
- <https://git.kernel.org/stable/c/97e06791368c01f0ad2a4b3269c2abe19485ca32>
- <https://git.kernel.org/stable/c/de02fc049352af5a9595f015511222d0a85c326b>
- <https://git.kernel.org/stable/c/6fe1cb312038516cb4d9fa089d700af7059f1a64>
- <https://git.kernel.org/stable/c/c0487a9c1e116cf349e2d1f302d9019670460858>
- <https://git.kernel.org/stable/c/9d5e7a46a9f6d8f503b41bfefef70659845f1679>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/sicherheitsluecken/cve-2026-63984/) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_