Answer in brief
CVE-2026-42557 records a Critical severity (CVSS 9.6) vulnerability in jupyterlab: Command linker attributes in HTML enable one-click command execution from untrusted content. The current sources do not mark it as known exploited. The current feed maps jupyterlab/jupyterlab (generic), jupyter/notebook (generic), jupyterlab (pip), notebook (pip). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 9.6. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps jupyterlab/jupyterlab (generic), jupyter/notebook (generic), jupyterlab (pip), notebook (pip). Check affected ranges and fixed versions before updating.
| Product | Affected versions | Fixed versions |
|---|---|---|
| cpe:2.3:a:jupyter:jupyterlab:*:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:a:jupyter:notebook:*:*:*:*:*:*:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| jupyterlab/jupyterlabgeneric | < 4.5.7 | Not reported |
| jupyter/notebookgeneric | >= 7.0.0, < 7.5.6 | Not reported |
| jupyterlabpip | <=4.5.6 | 4.5.7 |
| notebookpip | >=7.0.0,<=7.5.5 | 7.5.6 |
Published upstream
May 13, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 28, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jun 11, 2026
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.
Quoted source text, attributed separately from HOL analysis.