Bug 2477086 (CVE-2026-42557)

Summary:	CVE-2026-42557 jupyterlab: JupyterLab: Arbitrary code execution via deceptive button in HTML output
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	jkoehler, lphiri, rjohnson
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
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Doc Text:	A flaw was found in jupyterlab. This vulnerability allows a remote attacker to achieve arbitrary code execution by presenting a user with a specially crafted notebook containing a deceptive button in its pre-saved HTML cell output. When the user clicks this button, the CommandLinker component executes arbitrary JupyterLab commands without sufficient validation, leading to the execution of unauthorized code.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2490266, 2490268
Bug Blocks:

Description OSIDB Bzimport 2026-05-13 16:03:19 UTC

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.