CVE-2026-44727: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in jupyter-server jupyter_server
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.
CVE-2026-44727: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in jupyter-server jupyter_server
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.
CVSS v4.0
Score 9.3critical
Affected software
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Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-05-07T18:04:17.309Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
- Vendor Advisory Urls
- [{"url":"https://access.redhat.com/security/cve/CVE-2026-44727","vendor":"Red Hat"}]
Threat ID: 6a39a0f5eed863c81e6b01d7
Added to database: 06/22/2026, 20:54:13 UTC
Last enriched: 07/21/2026, 19:20:04 UTC
Last updated: 08/06/2026, 00:41:13 UTC
Views: 165
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