Is CVE-2026-102831 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-102831 being exploited in the wild.

How severe is CVE-2026-102831?

High severity, with a CVSS score of 8.1, published 29 September 2026.

Which products and versions are affected?

Project Jupyter Jupyter Notebook 7.5.0 to 7.6.2; Project Jupyter JupyterLab 4.5.0 to 4.5.10, 4.6.0 to 4.6.3; Project Jupyter JupyterLite Core 0.7.0 to 0.8.3; jupyterlab (PyPI) ECOSYSTEM:introduced=4.5.0,fixed=4.5.11,introduced=4.6.0,fixed=4.6.4, ECOSYSTEM:introduced=4.6.0,fixed=4.6.4; and 3 more.

Is there a fix for CVE-2026-102831?

Yes. jupyterlab (PyPI): upgrade to 4.6.4 or later; jupyterlite (PyPI): upgrade to 0.8.4 or later; jupyterlite-core (PyPI): upgrade to 0.8.4 or later; notebook (PyPI): upgrade to 7.6.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-102831 attacked?

It is attacked over the network.

Am I affected by CVE-2026-102831?

Check whether you run Project Jupyter Jupyter Notebook, Project Jupyter JupyterLab, Project Jupyter JupyterLite Core or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-102831: JupyterLab HTML output sanitization bypass via clipboard paste

CVE-2026-102831 · Severity: high · CVSS 8.1 · Published 2026-09-29

JupyterLab is an interactive computing environment used for data analysis and scientific research. When users paste code cells from the system clipboard with specific settings enabled, an attacker can inject malicious HTML that bypasses output sanitization and executes JavaScript in the browser within the authenticated user's session. This allows an attacker to compromise user sessions and steal sensitive data or execute arbitrary actions.

Technologies: Project Jupyter JupyterLab, jupyterlab (PyPI), jupyterlite-core (PyPI), notebook (PyPI). Vendors: Project Jupyter, PyPI.

Quick answers

Is CVE-2026-102831 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-102831 being exploited in the wild.
How severe is CVE-2026-102831?: High severity, with a CVSS score of 8.1, published 29 September 2026.
Which products and versions are affected?: Project Jupyter Jupyter Notebook 7.5.0 to 7.6.2; Project Jupyter JupyterLab 4.5.0 to 4.5.10, 4.6.0 to 4.6.3; Project Jupyter JupyterLite Core 0.7.0 to 0.8.3; jupyterlab (PyPI) ECOSYSTEM:introduced=4.5.0,fixed=4.5.11,introduced=4.6.0,fixed=4.6.4, ECOSYSTEM:introduced=4.6.0,fixed=4.6.4; and 3 more.
Is there a fix for CVE-2026-102831?: Yes. jupyterlab (PyPI): upgrade to 4.6.4 or later; jupyterlite (PyPI): upgrade to 0.8.4 or later; jupyterlite-core (PyPI): upgrade to 0.8.4 or later; notebook (PyPI): upgrade to 7.6.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-102831 attacked?: It is attacked over the network.
Am I affected by CVE-2026-102831?: Check whether you run Project Jupyter Jupyter Notebook, Project Jupyter JupyterLab, Project Jupyter JupyterLite Core or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

jupyterlab (PyPI): upgrade to 4.6.4 or later
```
pip install "jupyterlab>=4.6.4"
```
jupyterlite (PyPI): upgrade to 0.8.4 or later
```
pip install "jupyterlite>=0.8.4"
```
jupyterlite-core (PyPI): upgrade to 0.8.4 or later
```
pip install "jupyterlite-core>=0.8.4"
```
notebook (PyPI): upgrade to 7.6.3 or later
```
pip install "notebook>=7.6.3"
```

Technical details

The vulnerability exists in the system clipboard cell-paste handler, which fails to clear the metadata.trusted flag on pasted code cells. When useSystemClipboardForCells is active and pasteCodeCellsWithoutOutput is disabled, attacker-controlled cell JSON can preserve the trusted flag, allowing HTML output to bypass sanitization and execute script. The issue affects code cells in JupyterLab, Notebook, and JupyterLite Core across specific version ranges; markdown and raw cells are unaffected due to separate sanitization paths.

Affected products

Project Jupyter JupyterLab 4.5.0 to 4.5.10, 4.6.0 to 4.6.3
Project Jupyter Jupyter Notebook 7.5.0 to 7.6.2
Project Jupyter JupyterLite Core 0.7.0 to 0.8.3

Identifiers

CVE-2026-102831
GHSA-6966-vjj6-99xv
PYSEC-2026-4057
PYSEC-2026-4058
PYSEC-2026-4060
PYSEC-2026-4112

Timeline

2026-09-29: disclosed: CVE-2026-102831 published
2026-09-21: patched: Fix commits merged for JupyterLab

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.