---
cve: "CVE-2026-44727"
severity: "CRITICAL"
cvss: 9.3
epss: "0.4%"
vendor: "jupyter-server"
kev: false
exploited: false
published: "2026-06-22 19:56:56"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-09-21T10:43:43+02:00"
---

# CVE-2026-44727

> 9.3 CRITICAL · 🧪 PoC

## Beschreibung

Jupyter Server is the backend for Jupyter web applications. Prior to 2.20, the nbconvert HTTP handlers in jupyter_server render user-authored notebook HTML under the Jupyter origin without a sandbox directive in their Content-Security-Policy. Combined with nbconvert.HTMLExporter's default non-sanitizing behavior, a notebook carrying an HTML payload in a display_data output triggers stored XSS with cookie access, full /api/* authority, and kernel RCE. This vulnerability is fixed in 2.20.

## CVSS-Vektor

```
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Gering | warn |

## Patch verfügbar (OSV)

- 05a78ad879e69ef87e91b2714a8ebeb5ff9628a7 (Commit)
- 6cbee8d65e71abac851c4492fea987ad080580bd (Commit)

## Referenzen

- <https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-fcw5-x6j4-ccmp>
- <https://github.com/jupyter-server/jupyter_server/commit/6cbee8d65e71abac851c4492fea987ad080580bd>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-44727) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_