CVE-2026-44727: Jupyter Server is the backend for Jupyter web applications

Q: How do I fix CVE-2026-44727?

jupyter server: upgrade to 2.20.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-44727 being exploited?

CVE-2026-44727 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-44727 affect?

CVE-2026-44727 affects jupyter server. Severity is medium (CVSS 5.4). 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-Polic

Q: How urgent is CVE-2026-44727?

Priority 28/100. No elevated risk signals yet.

Routine

MEDIUM 5.4UPGRADE

CVE-2026-44727 is a medium-severity flaw (CVSS 5.4) affecting jupyter server. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	5.4 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.4% (top 62%)
CISA exploited list	No
Weakness	CWE-79, CWE-1021
Published	2026-06-22
Last modified	2026-10-25

Publisher (CNA): GitHub, Inc. · Vendor: jupyter

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-22 21:16 UTCPublished CVE record published
2026-10-25 23:10 UTCUpdated Record last modified

jupyter jupyter server UPGRADE

Affected: < 2.20.0

Fixed in: 2.20.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy jupyter-server || rpm -q jupyter-server || jupyter-server --version

2. UPGRADE to 2.20.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade jupyter-server

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade jupyter-server

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-44727?

jupyter server: upgrade to 2.20.0. Exact commands for each OS are on this page.

Is CVE-2026-44727 being exploited?

CVE-2026-44727 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-44727 affect?

CVE-2026-44727 affects jupyter server. Severity is medium (CVSS 5.4). 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-Polic

How urgent is CVE-2026-44727?

Priority 28/100. No elevated risk signals yet.

Software pages

Jupyter vulnerabilities

References

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