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🛡️ CVE-2026-40171 — jupyter-base-notebook

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-601 NVD
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Jupyter Notebook Vulnerable to Authentication Token Theft via CommandLinker XSS

Impact

A stored Cross-Site Scripting (XSS) vulnerability in Jupyter Notebook allows attackers to steal authentication tokens from users who open malicious notebook files and interact with elements that the attacker can make look indistinguishable from legitimate controls (single click interaction).

The vulnerability enables complete account takeover through the Jupyter REST API, allowing the attacker to:

1. Read all files

2. Modify/create files

3. Access running kernels and execute arbitrary code

4. Create terminals for shell access

Patches

Jupyter Notebook 7.5.6 and JupyterLab 4.5.7 include patches for this vulnerability.

Workarounds

The help extension can be disabled via CLI:

```

jupyter labextension disable @jupyter-notebook/help-extension

jupyter labextension disable @jupyterlab/help-extension

```

Hardening

The patched versions include a toggle to disable the command linker functionality altogether, for example via overrides.json:

```json

{

"@jupyterlab/apputils-extension:sanitizer": {

"allowCommandLinker": false

}

}

```

Resources

  • https://jupyterlab.readthedocs.io/en/latest/user/commands.html#commands-in-markdown-output-and-files

Acknowledgments

Reported by Daniel Teixeira - NVIDIA AI Red Team

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs administrative privileges on the target. A user must actively cooperate. Rated impact: confidentiality high, integrity high, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Attack requirements: None — no deployment-specific condition has to hold.
  • Privileges required: High — administrative rights are needed first.
  • User interaction: Active — the victim has to cooperate with the attack.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

CVE-2026-40171 is classified as CWE-601: Open Redirect. A redirect target is taken from user input, so a trusted link can send the visitor to an attacker's site.

Affected software

CVE-2026-40171 is recorded against 7 packages.

  • @jupyter-notebook/help-extension
  • @jupyterlab/help-extension
  • jupyter-base-notebook
  • jupyter-notebook
  • jupyterlab (fixed in 4.5.7)
  • notebook (from 7.0.0 up to 7.5.6)
  • unknown

Timeline and source

Published on 30 April 2026 and last revised on 13 July 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

github.com (Web)
nvd.nist.gov (Advisory)
github.com (Package)
jupyterlab.readthedocs.io (Web)

Same weakness in other software

These advisories are the same class of weakness (CWE-601: Open Redirect) in other software:

CVE-2026-40171 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CWE CWE-601
Public Exploit ✅ No
Source NVD
Published 2026-04-30
Updated 2026-08-20
Modified 2026-07-13
Fix URL N/A

Affected Packages

Software From version Fixed in
@jupyter-notebook/help-extension — —
@jupyterlab/help-extension — —
jupyter-base-notebook — —
jupyter-notebook — —
jupyterlab — 4.5.7
notebook 7.0.0 7.5.6
unknown — —

Site Security Check

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