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.
Affected products
jupyter: jupyterlab; jupyter: notebook
References6
- github.com/jupyterlab/jupyterlab/security/advisories/GHSA-mqcg-… MitigationVendor Advisory
- access.redhat.com/errata/RHSA-2026:43038
- access.redhat.com/errata/RHSA-2026:60520
- access.redhat.com/security/cve/CVE-2026-42557
- bugzilla.redhat.com/show_bug.cgi?id=2477086
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42557…
Metrics
- CVSS 3.1
-
9.6
CRITICAL
Score source: NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H - CVSS 4.0
-
8.6
HIGH
Score source: CNA
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 0% percentile: 42 · as of 14 November 2026
- CWE
- CWE-79
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.