CVE-2026-44727
CRITICAL EPSS 5.9%
Published Jun 22, 20261w ago · Modified Jun 23, 20261w ago
9.3 CVSS 4.0
Published Jun 22, 2026 1w ago
Last Modified Jun 23, 2026 1w ago
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 Details
Base Score
Exploitability
Impact
Vector string
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Attack Vector Network
Attack Complexity Low
Privileges Required Low
User Interaction A
Scope X
Threat Intelligence
EPSS Exploit Probability
5.9% percentile
Exploit & Patch Status
No Known Exploit
No Patch Available
Weaknesses 2
CWE-1021
CWE-79 Cross-site Scripting Injection
References 2
- github.com https://github.com/jupyter-server/jupyter_server/commit/6cbee8d65e71abac851c4492fea987ad080580bd
- github.com https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-fcw5-x6j4-ccmp
Remediation
No remediation data recorded yet
Check vendor advisories and the NVD entry for patch availability.