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BIT-jupyterlab-2026-40171 — Jupyter Notebook and JupyterLab token theft via stored XSS in help command linker

Affected: Bitnami: jupyterlab

An attacker can craft a malicious notebook file containing elements that appear indistinguishable from legitimate controls and trigger execution when a user interacts with them. Successful exploitation allows theft of the user's authentication token and complete takeover of the Jupyter session through the REST API, including reading files, creating or modifying files, accessing kernels to execute arbitrary code, and creating terminals for shell access. This issue has been fixed in Notebook 7.5.6, JupyterLab 4.5.7, @jupyter-notebook/help-extension 7.5.6, and @jupyterlab/help-extension 4.5.7. As a workaround, disable the affected help extensions or set allowCommandLinker to false in the sanitizer configuration.

BREW-jupyterlab-CVE-2026-40171 — Jupyter Notebook Vulnerable to Authentication Token Theft via CommandLinker XSS

Affected: Homebrew: jupyterlab

### 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

Withdrawn: CLEANSTART-2026-GG76429 — Security fixes in tensorflow-gpu-jupyter 2.21.0-r5

Withdrawn by the publisher.

Affected: CleanStart: tensorflow-gpu-jupyter

Package tensorflow-gpu-jupyter version 2.21.0-r5 fixes 28 vulnerabilities: ghsa-rch3-82jr-f9w9, ghsa-mqcg-5x36-vfcg, ghsa-37w4-hwhx-4rc4, ghsa-mf9v-mfxr-j63j, ghsa-5mrq-x3x5-8v8f...

EUVD-2026-309099

fkie_cve-2026-40171

GHSA-rch3-82jr-f9w9 — Jupyter Notebook Vulnerable to Authentication Token Theft via CommandLinker XSS

Affected: npm: @jupyter-notebook/help-extension, PyPI: notebook, PyPI: jupyterlab, npm: @jupyterlab/help-extension

### Impact

### 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

openSUSE-SU-2026:10748-1 — jupyter-jupyterlab-4.5.7-1.1 on GA media

jupyter-jupyterlab-4.5.7-1.1 on GA media

PYSEC-2026-2538 — Jupyter Notebook Vulnerable to Authentication Token Theft via CommandLinker XSS

Affected: PyPI: jupyterlab

### Impact

### 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

RHSA-2026:43038 — Red Hat Security Advisory: Migration Toolkit for Applications

jupyter-server: jupyter-server: Sensitive data exposure via path traversal vulnerability fast-uri: fast-uri: URI authority bypass due to improper delimiter handling fast-uri: fast-uri: Security policy bypass due to improper Unicode hostname canonicalization golang.org/x/net/html: golang.org/x/net/html: Arbitrary code execution via Cross-Site Scripting golang.org/x/net/html: golang: golang.org/x/net/html: Cross-Site Scripting via HTML parsing bypass python-dotenv: python-dotenv: Arbitrary file overwrite via symbolic link following mistune: Mistune: Regular Expression Denial of Service (ReDoS) via crafted Markdown input net: golang: Go net package: Denial of Service via long CNAME response in LookupCNAME aiohttp: AIOHTTP: Arbitrary code execution via untrusted input to CookieJar.load() jupyter-server: Jupyter Server: Unauthorized File Access via Path Traversal Vulnerability net/mail: golang: Go net/mail: Denial of Service via crafted email inputs golang.org/x/net/idna: golang: net/http: golang.org/x/net/idna: Privilege escalation via incorrect Punycode label processing jupyter-server: Jupyter Server: Cross-Origin Resource Sharing (CORS) bypass via improper Origin header validation Jupyter Notebook: JupyterLab: @jupyter-notebook/help-extension: @jupyterlab/help-extension: Jupyter Notebook and JupyterLab: Session takeover via stored cross-site scripting jupyterlab: JupyterLab: Arbitrary code execution due to improper enforcement of extension allow-list net/mail: golang: net/mail…

UBUNTU-CVE-2026-40171

Affected: Ubuntu:18.04:LTS: jupyter-notebook, Ubuntu:20.04:LTS: jupyter-notebook, Ubuntu:Pro:22.04:LTS: jupyter-notebook, Ubuntu:Pro:24.04:LTS: jupyter-notebook, Ubuntu:25.10: jupyter-notebook, Ubuntu:26.04:LTS: jupyter-notebook

In Jupyter Notebook versions 7.0.0 through 7.5.5, JupyterLab versions 4.5.6 and earlier, and the corresponding @jupyter-notebook/help-extension and @jupyterlab/help-extension packages before 7.5.6 and 4.5.7, a stored cross-site scripting issue in the help command linker can be chained with attacker-controlled notebook content to steal authentication tokens with a single click. An attacker can craft a malicious notebook file containing elements that appear indistinguishable from legitimate controls and trigger execution when a user interacts with them. Successful exploitation allows theft of the user's authentication token and complete takeover of the Jupyter session through the REST API, including reading files, creating or modifying files, accessing kernels to execute arbitrary code, and creating terminals for shell access. This issue has been fixed in Notebook 7.5.6, JupyterLab 4.5.7, @jupyter-notebook/help-extension 7.5.6, and @jupyterlab/help-extension 4.5.7. As a workaround, disable the affected help extensions or set allowCommandLinker to false in the sanitizer configuration.