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CVE Vulnerability Details :
CVE-2026-44727
PUBLISHED
More InfoOfficial Page
Assigner-GitHub_M
Assigner Org ID-a0819718-46f1-4df5-94e2-005712e83aaa
View Known Exploited Vulnerability (KEV) details
Published At-22 Jun, 2026 | 19:56
Updated At-30 Jun, 2026 | 12:10
Rejected At-
▼CVE Numbering Authority (CNA)
Jupyter Server: Stored XSS in `NbconvertFileHandler` / `NbconvertPostHandler` via missing `sandbox` CSP

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 Products
Vendor
jupyter-server
Product
jupyter_server
Versions
Affected
  • < 2.20
Problem Types
TypeCWE IDDescription
CWECWE-79CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWECWE-1021CWE-1021: Improper Restriction of Rendered UI Layers or Frames
Type: CWE
CWE ID: CWE-79
Description: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Type: CWE
CWE ID: CWE-1021
Description: CWE-1021: Improper Restriction of Rendered UI Layers or Frames
Metrics
VersionBase scoreBase severityVector
4.09.3CRITICAL
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
Version: 4.0
Base score: 9.3
Base severity: CRITICAL
Vector:
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
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions
Configurations
Workarounds
Exploits
Credits
Timeline
EventDate
Replaced By
Rejected Reason
References
HyperlinkResource
https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-fcw5-x6j4-ccmp
x_refsource_CONFIRM
https://github.com/jupyter-server/jupyter_server/commit/6cbee8d65e71abac851c4492fea987ad080580bd
x_refsource_MISC
Hyperlink: https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-fcw5-x6j4-ccmp
Resource:
x_refsource_CONFIRM
Hyperlink: https://github.com/jupyter-server/jupyter_server/commit/6cbee8d65e71abac851c4492fea987ad080580bd
Resource:
x_refsource_MISC
▼Authorized Data Publishers (ADP)
1. CISA ADP Vulnrichment
Affected Products
Metrics
VersionBase scoreBase severityVector
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions
Configurations
Workarounds
Exploits
Credits
Timeline
EventDate
Replaced By
Rejected Reason
References
HyperlinkResource
2. jupyter-server: Jupyter Server: Remote Code Execution via stored Cross-Site Scripting in nbconvert handlers

A flaw was found in Jupyter Server. The nbconvert HTTP handlers in Jupyter Server render user-authored notebook HTML without a sandbox directive in their Content-Security-Policy. This, combined with nbconvert.HTMLExporter's default non-sanitizing behavior, allows a notebook containing an HTML payload to trigger a stored Cross-Site Scripting (XSS) vulnerability. A remote attacker could exploit this to gain cookie access, full API authority, and achieve kernel Remote Code Execution (RCE).

Affected Products
Vendor
Red Hat, Inc.Red Hat
Product
Migration Toolkit for Applications 8
CPEs
  • cpe:/a:redhat:migration_toolkit_applications:8
Default Status
affected
Vendor
Red Hat, Inc.Red Hat
Product
Red Hat OpenShift AI (RHOAI)
CPEs
  • cpe:/a:redhat:openshift_ai
Default Status
affected
Problem Types
TypeCWE IDDescription
CWECWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Type: CWE
CWE ID: CWE-79
Description: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Metrics
VersionBase scoreBase severityVector
3.19.0CRITICAL
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
Version: 3.1
Base score: 9.0
Base severity: CRITICAL
Vector:
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
Metrics Other Info
Red Hat severity rating
value:
Important
namespace:
https://access.redhat.com/security/updates/classification/
Impacts
CAPEC IDDescription
Solutions
Configurations
Workarounds
Exploits
Credits
Timeline
EventDate
Reported to Red Hat.2026-06-22 21:00:50
Made public.2026-06-22 19:56:56
Event: Reported to Red Hat.
Date: 2026-06-22 21:00:50
Event: Made public.
Date: 2026-06-22 19:56:56
Replaced By
Rejected Reason
References
HyperlinkResource
https://access.redhat.com/security/cve/CVE-2026-44727
vdb-entry
x_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2491516
issue-tracking
x_refsource_REDHAT
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-44727.json
x_sadp-csaf-vex
Hyperlink: https://access.redhat.com/security/cve/CVE-2026-44727
Resource:
vdb-entry
x_refsource_REDHAT
Hyperlink: https://bugzilla.redhat.com/show_bug.cgi?id=2491516
Resource:
issue-tracking
x_refsource_REDHAT
Hyperlink: https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-44727.json
Resource:
x_sadp-csaf-vex
Details not found