CVE-2026-42557: jupyterlab is an extensible environment for interactive and reproducible computing, based on the Jupyter Noteb

This month

CRITICAL 9.6UPGRADEUPGRADE

CVE-2026-42557 is a critical-severity flaw (CVSS 9.6) affecting jupyterlab, notebook. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

jupyterlab is an extensible environment for interactive and reproducible computing, based on the Jupyter Notebook Architecture. Prior to 4.5.7, JupyterLab's HTML sanitizer allowlists data-commandlinker-command and data-commandlinker-args on button elements, while CommandLinker listens for all click events on document.body and executes the named command without checking whether the element came from trusted JupyterLab UI. A notebook with a pre-sav

Why this priority

Critical severity

A fixed release or distro patch exists.

Risk facts

CVSS score	9.6 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.4% (top 69%)
CISA exploited list	No
Weakness	CWE-79
Published	2026-05-13
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

2026-05-13 16:16 UTCPublished CVE record published
2026-10-25 23:10 UTCUpdated Record last modified

jupyter jupyterlab UPGRADE

Affected: < 4.5.7

Fixed in: 4.5.7

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy jupyterlab || rpm -q jupyterlab || jupyterlab --version

2. UPGRADE to 4.5.7 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade jupyterlab

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade jupyterlab

Note

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

jupyter notebook UPGRADE

Affected: >= 7.0.0 and < 7.5.6

Fixed in: 7.5.6

Safe to downgrade to: a release before 7.0.0

1. Check installed version

apt-cache policy notebook || rpm -q notebook || notebook --version

2. UPGRADE to 7.5.6 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade notebook

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade notebook

Note

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

3. If no update is available yet, DOWNGRADE to a release before 7.0.0 (Debian / Ubuntu)

apt-cache madison notebook sudo apt install notebook=<VERSION_BEFORE_7.0.0> sudo apt-mark hold notebook

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list notebook sudo dnf downgrade notebook-<VERSION_BEFORE_7.0.0> sudo dnf versionlock add notebook

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

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-2026-42557?

jupyterlab: upgrade to 4.5.7; notebook: upgrade to 7.5.6. Exact commands for each OS are on this page.

Is CVE-2026-42557 being exploited?

CVE-2026-42557 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-2026-42557 affect?

CVE-2026-42557 affects jupyterlab, notebook. Severity is critical (CVSS 9.6). jupyterlab is an extensible environment for interactive and reproducible computing, based on the Jupyter Notebook Architecture. Prior to 4.5.7, JupyterLab's HTML sanitizer allowlists data-commandlinker-command and data-commandlinker-args on

How urgent is CVE-2026-42557?

Priority 41/100. Critical severity

Software pages

Jupyter vulnerabilities

References

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