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CVE-2026-44727

CVE-2026-44727 · Jupyter Server: Stored XSS in `NbconvertFileHandler` / `NbconvertPostHandler` via missing `sandbox` CSP

This page contains facts from public vulnerability sources. Check the original advisory before updating.

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 9.3 · Critical · EPSS 0.4% · Fix available

Published
Updated

Stack: system · python

Affected products and versions

  • jupyter_server

    Versions
    • < 2.20: Affected

    No fix published

  • jupyter-server Debian:12

    Versions
    • 1.23.3-1
    • 1.23.3-2
    • 2.14.0-1
    • 2.14.2-1
    • 2.14.2-2
    • 2.14.2-3
    • 2.14.2-4
    • 2.14.2-5
    • 2.15.0-1
    • 2.17.0-1
    • 2.20.0-1
    • 2.20.0-2
    • 2.20.0-3
    • 2.9.1-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • jupyter-server Debian:13

    Versions
    • 2.15.0-1
    • 2.17.0-1
    • 2.20.0-1
    • 2.20.0-2
    • 2.20.0-3
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • jupyter-server Debian:14

    Versions
    • 2.15.0-1
    • 2.17.0-1
    Affected ranges
    • ECOSYSTEM: < 2.20.0-1

    Update to 2.20.0-1

  • jupyter-server PyPI

    Versions
    • 0.0.0
    • 0.0.1
    • 0.0.2
    • 0.0.3
    • 0.0.4
    • 0.0.5
    • 0.1.0
    • 0.1.1
    • 0.2.0
    • 0.2.1
    • 0.3.0
    • 1.0.0
    • 1.0.0rc0
    • 1.0.0rc1
    • 1.0.0rc10
    • 1.0.0rc11
    • 1.0.0rc12
    • 1.0.0rc13
    • 1.0.0rc14
    • 1.0.0rc15
    • 1.0.0rc16
    • 1.0.0rc2
    • 1.0.0rc3
    • 1.0.0rc4
    • 1.0.0rc5
    • 1.0.0rc6
    • 1.0.0rc7
    • 1.0.0rc8
    • 1.0.0rc9
    • 1.0.1
    • 1.0.10
    • 1.0.11
    • 1.0.2
    • 1.0.3
    • 1.0.4
    • 1.0.5
    • 1.0.6
    • 1.0.7
    • 1.0.8
    • 1.0.9
    • 1.1.0
    • 1.1.1
    • 1.1.2
    • 1.1.3
    • 1.1.4
    • 1.10.0
    • 1.10.1
    • 1.10.2
    • 1.11.0
    • 1.11.1
    • 1.11.2
    • 1.12.0
    • 1.12.1
    • 1.13.0
    • 1.13.1
    • 1.13.2
    • 1.13.3
    • 1.13.4
    • 1.13.5
    • 1.15.0
    • 1.15.1
    • 1.15.2
    • 1.15.3
    • 1.15.4
    • 1.15.5
    • 1.15.6
    • 1.16.0
    • 1.17.0
    • 1.17.1
    • 1.18.0
    • 1.18.1
    • 1.19.0
    • 1.19.1
    • 1.2.0
    • 1.2.1
    • 1.2.2
    • 1.2.3
    • 1.21.0
    • 1.23.0
    • 1.23.1
    • 1.23.2
    • 1.23.3
    • 1.23.4
    • 1.23.5
    • 1.23.6
    • 1.24.0
    • 1.3.0
    • 1.4.0
    • 1.4.1
    • 1.5.0
    • 1.5.1
    • 1.6.0
    • 1.6.1
    • 1.6.2
    • 1.6.3
    • 1.6.4
    • 1.7.0
    • 1.7.0a1
    • 1.7.0a2
    • 1.8.0
    • 1.9.0
    • 2.0.0
    • 2.0.0a0
    • 2.0.0a1
    • 2.0.0a2
    • 2.0.0b0
    • 2.0.0b1
    • 2.0.0rc0
    • 2.0.0rc1
    • 2.0.0rc2
    • 2.0.0rc3
    • 2.0.0rc4
    • 2.0.0rc5
    • 2.0.0rc6
    • 2.0.0rc7
    • 2.0.0rc8
    • 2.0.1
    • 2.0.2
    • 2.0.3
    • 2.0.4
    • 2.0.5
    • 2.0.6
    • 2.0.7
    • 2.1.0
    • 2.10.0
    • 2.10.1
    • 2.11.0
    • 2.11.1
    • 2.11.2
    • 2.12.0
    • 2.12.1
    • 2.12.2
    • 2.12.3
    • 2.12.4
    • 2.12.5
    • 2.13.0
    • 2.14.0
    • 2.14.1
    • 2.14.2
    • 2.15.0
    • 2.16.0
    • 2.17.0
    • 2.18.0
    • 2.18.1
    • 2.18.2
    • 2.19.0
    • 2.2.0
    • 2.2.1
    • 2.3.0
    • 2.4.0
    • 2.5.0
    • 2.6.0
    • 2.7.0
    • 2.7.1
    • 2.7.2
    • 2.7.3
    • 2.8.0
    • 2.9.0
    • 2.9.1
    Affected ranges
    • ECOSYSTEM: < 2.20.0

    Update to 2.20.0

  • jupyter-server Ubuntu:22.04:LTS

    Versions
    • 1.2.2-1
    • 1.13.1-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • jupyter-server Ubuntu:24.04:LTS

    Versions
    • 1.23.3-1
    • 1.23.3-2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • jupyter-server Ubuntu:25.10

    Versions
    • 2.14.2-5
    • 2.15.0-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • jupyter-server Ubuntu:26.10

    Versions
    • 2.17.0-1
    • 2.20.0-3
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • jupyter-server Ubuntu:26.04:LTS

    Versions
    • 2.15.0-1
    • 2.17.0-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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