CVE-2026-44727
Published:June 22, 2026
Updated:June 29, 2026
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.
Affected Packages
jupyter_server (CONDA):
Affected version(s) >=0.0.2 <2.20.0Fix Suggestion:
Update to version 2.20.0https://github.com/jupyter-server/jupyter_server.git (GITHUB):
Affected version(s) >=v1.6.2 <v2.20.0Fix Suggestion:
Update to version v2.20.0jupyter_server (PYTHON):
Affected version(s) >=0.0.0 <2.20.0Fix Suggestion:
Update to version 2.20.0jupyter-server (PYTHON):
Affected version(s) >=0.0.0 <2.20.0Fix Suggestion:
Update to version 2.20.0jupyter-server (PYTHON):
Affected version(s) >=0.0.0 <2.20.0Fix Suggestion:
Update to version 2.20.0Related Resources (3)
Do you need more information?
Contact UsCVSS v4
Base Score:
9.3
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
LOW
User Interaction
ACTIVE
Vulnerable System Confidentiality
HIGH
Vulnerable System Integrity
HIGH
Vulnerable System Availability
HIGH
Subsequent System Confidentiality
HIGH
Subsequent System Integrity
HIGH
Subsequent System Availability
HIGH
CVSS v3
Base Score:
9
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Weakness Type (CWE)
EPSS
Base Score:
0.16