CVE-2026-44727 Details
Description
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.
A stored cross-site scripting vulnerability has been identified in Jupyter Server versions prior to 2.20.0. The issue arises in the nbconvert HTTP handlers, which render user-authored notebook HTML without a sandbox directive in the Content-Security-Policy. This omission, combined with nbconvert.HTMLExporter's default non-sanitizing behavior, allows a notebook containing an HTML payload in the display_data output to execute JavaScript in the Jupyter origin. The executed script can access cookies, interact with the Jupyter API, and execute code on the kernel, leading to remote code execution.
Users can update to Jupyter Server version 2.20.0 or later, where this vulnerability has been patched. For those unable to update, adding a Content-Security-Policy sandbox directive through the Jupyter server configuration can mitigate the issue.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jun 23, 2026References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-1021 | Improper Restriction of Rendered UI Layers or Frames | [email protected] |
| CWE-79 | Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') | redhat-SADP |
| CWE-79 | Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') | [email protected] |
| CWE-79 | Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| jupyter jupyter server | < 2.20.0 |
CPE
Remediation
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Change History
8 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Aug 28, 2026 | CVE Modified | redhat-SADP |
| Aug 28, 2026 | CVE Modified | [email protected] |
| Jul 22, 2026 | CVE Modified | redhat-SADP |
| Jul 15, 2026 | CVE Modified | redhat-SADP |
| Jun 30, 2026 | CVE Modified | redhat-SADP |
| Jun 26, 2026 | Initial Analysis | [email protected] |
| Jun 23, 2026 | CVE Modified | CISA-ADP |
| Jun 22, 2026 | New CVE Received | [email protected] |