CVE-2026-42266: JupyterLab is an extensible environment for interactive and reproducible computing, based on the Jupyter Noteb

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HIGH 8.8UPGRADE

CVE-2026-42266 is a high-severity flaw (CVSS 8.8) affecting jupyterlab. 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. From 4.0.0 to 4.5.6, the allow-list of extensions that can be installed from PyPI Extension Manager (allowed_extensions_uris) is not correctly enforced by JupyterLab. The PyPI Extension Manager was not contained to packages listed on the default PyPI index. This vulnerability is fixed in 4.5.7.

Why this priority

High severity
EPSS top 7%: very likely to be exploited

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	5.7% (top 7%)
CISA exploited list	No
Weakness	CWE-88, CWE-602
Published	2026-05-13
Last modified	2026-08-28

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

Last updated 2026-08-28 · 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
2026-08-28 16:17 UTCUpdated Record last modified

jupyter jupyterlab UPGRADE

Affected: >= 4.0.0 and < 4.5.7

Fixed in: 4.5.7

Safe to downgrade to: a release before 4.0.0

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.

3. If no update is available yet, DOWNGRADE to a release before 4.0.0 (Debian / Ubuntu)

apt-cache madison jupyterlab sudo apt install jupyterlab=<VERSION_BEFORE_4.0.0> sudo apt-mark hold jupyterlab

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

dnf --showduplicates list jupyterlab sudo dnf downgrade jupyterlab-<VERSION_BEFORE_4.0.0> sudo dnf versionlock add jupyterlab

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-2026-42266?

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

Is CVE-2026-42266 being exploited?

CVE-2026-42266 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-2026-42266 affect?

CVE-2026-42266 affects jupyterlab. Severity is high (CVSS 8.8). JupyterLab is an extensible environment for interactive and reproducible computing, based on the Jupyter Notebook Architecture. From 4.0.0 to 4.5.6, the allow-list of extensions that can be installed from PyPI Extension Manager (allowed_ext

How urgent is CVE-2026-42266?

Priority 54/100. High severity; EPSS top 7%: very likely to be exploited

Software pages

Jupyter vulnerabilities · PyPI packages vulnerabilities

Related CVEs

CVE-2026-42557 CRITICAL 9.6 UPGRADE UPGRADE jupyterlab is an extensible environment for interactive and reproducible computing, based on the Jupyter Noteb

References

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