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CVE-2026-42557

Jupyter Jupyterlab cross-site scripting (XSS)

9.6 CRITICALEPSS 0.71%
  1. Published13 May 2026

Description

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-saved HTML cell output containing a deceptive button can trigger arbitrary JupyterLab commands - including arbitrary code execution - on a single user click, without any code being submitted for execution by the user. This vulnerability is fixed in 4.5.7.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionRequired
ScopeChanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

Affected products

Jupyter Jupyterlab< 4.5.7
Jupyter Notebook≥ 7.0.0 < 7.5.6

Remediation

Fixed in
Jupyter Jupyterlab≥ 4.5.7
Jupyter Notebook≥ 7.5.6

References

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Frequently asked

Is CVE-2026-42557 being actively exploited?

CVE-2026-42557 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.71%.

How severe is CVE-2026-42557?

CVE-2026-42557 has a CVSS 3.1 base score of 9.6, rated critical. EPSS estimates a 0.71% probability of exploitation.

Which products are affected by CVE-2026-42557?

Affected products include Jupyter Jupyterlab, Jupyter Notebook.

How do I fix CVE-2026-42557?

Upgrade affected software to a fixed version, for example Jupyter Jupyterlab 4.5.7, Jupyter Notebook 7.5.6 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-42557 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.