CVE-2026-42557Network attack vector

Arbitrary code execution via untrusted command buttons

Published May 13, 2026 · Updated May 13, 2026

Cross-site scripting in Project Jupyter JupyterLab before 4.5.7 and Jupyter Notebook 7.0.0 through 7.5.5 allows attackers to execute code. The HTML sanitizer preserves data-commandlinker-command and data-commandlinker-args on untrusted buttons, and CommandLinker executes the named command from any body click without verifying trusted UI origin. A victim must open the shared notebook or Markdown file and click the deceptive control; one click runs available-kernel code, while additional clicks and Chromium clipboard access can expose the terminal.

CVSS severity8.6
High
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in Project Jupyter JupyterLab before 4.5.7 and Jupyter Notebook 7.0.0 through 7.5.5 allows attackers to execute code. The HTML sanitizer preserves data-commandlinker-command and data-commandlinker-args on untrusted buttons, and CommandLinker executes the named command from any body click without verifying trusted UI origin. A victim must open the shared notebook or Markdown file and click the deceptive control; one click runs available-kernel code, while additional clicks and Chromium clipboard access can expose the terminal.

The record

CVE
CVE-2026-42557
Published
May 13, 2026
Updated
May 13, 2026
Vendor
Project Jupyter
Product
JupyterLab
Classifications
CWE-79, T1204.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 13, 2026CVE publishedPublication date reported by the CVE source.
  2. May 13, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 4.5.7

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Project Jupyter · JupyterLabversion=< 4.5.7
Project Jupyter · Jupyter Notebookversion=>= 7.0.0, < 7.5.6

Published CVSS scores

9.6NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
8.8Red HatCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
8.6GitHubCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1204.002User Execution: Malicious File

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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