CVE-2021-41247Network attack vector

Persistent single-user access via shared PageConfig token

Published Nov 4, 2021 · Updated Aug 4, 2024

Insufficient session expiration in JupyterHub 1.0.0 through 1.4.2 allows remote authenticated users to retain single-user access. JupyterLab loads JUPYTERHUB_API_TOKEN into shared PageConfig data, so another open tab can restore fresh single-user credentials after logout. The condition requires multiple JupyterLab tabs in one browser session; Hub authentication ends, but the browser retains access to the user's server.

CVSS severity7.5
High
EPSS probability0.80%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Insufficient session expiration in JupyterHub 1.0.0 through 1.4.2 allows remote authenticated users to retain single-user access. JupyterLab loads JUPYTERHUB_API_TOKEN into shared PageConfig data, so another open tab can restore fresh single-user credentials after logout. The condition requires multiple JupyterLab tabs in one browser session; Hub authentication ends, but the browser retains access to the user's server.

The record

CVE
CVE-2021-41247
Published
Nov 4, 2021
Updated
Aug 4, 2024
Vendor
Project Jupyter
Product
JupyterHub
Classifications
CWE-613
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 4, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=>= 1.0.0, < 1.5.0 - jupyterhub (pip)
  2. Affected versionversion=< 1.2.0 - jupyterhub (helm)

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Project Jupyter · JupyterHubversion=>= 1.0.0, < 1.5.0 - jupyterhub (pip); version=< 1.2.0 - jupyterhub (helm)

Published CVSS scores

3.5GitHubCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:N
5.0NVDAV:N/AC:L/Au:N/C:N/I:P/A:N
7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-613Insufficient Session Expiration

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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