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BREW-jupyterlab-CVE-2026-40934 — Jupyter Server's Authentication Cookies Remain Valid After Password Reset and Server Restart

Affected: Homebrew: jupyterlab

## Summary

A persistent cookie secret vulnerability allows authenticated users to maintain indefinite access even after password changes.

The cookie secret used to sign authentication cookies is stored in a permanent file (`~/.local/share/jupyter/runtime/jupyter_cookie_secret`) that is never automatically rotated or cleared, allowing stolen or compromised cookies to remain valid indefinitely regardless of password resets.

## PoC

- Start a Jupyter server with password authentication: `jupyter server password`, `jupyter server` - Log in with the password and capture the authentication cookie (e.g., just login with a browser). - Change the password to revoke access: `jupyter server password` - Restart the server - Use the old stolen cookie => remains valid and provides full authenticated access.

## Impact

- All jupyter-server deployments using password authentication where security incidents may occur - Multi-user systems where one user's compromised session should be revocable by administrators - Shared or public-facing Jupyter servers where credential rotation is a security requirement - Any deployment where password changes are expected to revoke existing sessions

## Patches

Jupyter Server 2.18+

## Workaround

```bash rm ~/.local/share/jupyter/runtime/jupyter_cookie_secret # Then restart the server ```

Withdrawn: CLEANSTART-2026-GG76429 — Security fixes in tensorflow-gpu-jupyter 2.21.0-r5

Withdrawn by the publisher.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-2026-308951

fkie_cve-2026-40934

Jupyter Server is the backend for Jupyter web applications. In versions 2.17.0 and earlier, the secret used to sign authentication cookies is persisted to a static file at ~/.local/share/jupyter/runtime/jupyter_cookie_secret and is never rotated when a user changes their password. After a password reset and server restart, any previously issued authentication cookie remains cryptographically valid because the signing key has not changed. An attacker who has captured a session cookie through any means retains full authenticated access to the server regardless of subsequent password changes. This affects deployments using password-based authentication, particularly shared or public-facing servers where credential rotation is expected to revoke existing sessions. This issue has been fixed in version 2.18.0.

GHSA-5mrq-x3x5-8v8f — Jupyter Server's Authentication Cookies Remain Valid After Password Reset and Server Restart

Affected: PyPI: jupyter-server

## Summary

A persistent cookie secret vulnerability allows authenticated users to maintain indefinite access even after password changes.

## PoC

## Impact

## Patches

Jupyter Server 2.18+

## Workaround

```bash rm ~/.local/share/jupyter/runtime/jupyter_cookie_secret # Then restart the server ```

OESA-2026-4080 — python-jupyter-server security update

Affected: openEuler:24.03-LTS-SP4: python-jupyter-server

The backend for Jupyter web applications Security Fix(es):

Jupyter Server is the backend for Jupyter web applications. In jupyter_server versions through 2.17.0, the next query parameter in the login flow is insufficiently validated in `LoginFormHandler._redirect_safe()`, which allows redirects to arbitrary external domains via values such as `///example.com`. An attacker can use a crafted login URL to redirect users to a malicious site and facilitate phishing attacks. This issue is fixed in version 2.18.0.(CVE-2025-61669)

Jupyter Server is the backend for Jupyter web applications. In versions 2.17.0 and earlier, a path traversal vulnerability in the REST API allows an authenticated user to escape the configured root_dir and access sibling directories whose names begin with the same prefix as the root_dir. For example, with a root_dir named "test", the API permits access to a sibling directory named "testtest" through a crafted request to the /api/contents endpoint using encoded path components. An attacker can read, write, and delete files in affected sibling directories. Multi-tenant deployments using predictable naming schemes are particularly at risk, as a user with a directory named "user1" could access directories for user10 through user19 and beyond. A user who can choose a single-character folder name could gain access to a significant number of sibling directories.

Version 2.18.0 contains a fix. As a workaround, ensure folder nam…

openSUSE-SU-2026:10710-1 — python311-jupyter-server-2.18.1-1.1 on GA media

python311-jupyter-server-2.18.1-1.1 on GA media

PYSEC-2026-69

Affected: PyPI: jupyter-server

UBUNTU-CVE-2026-40934

Affected: Ubuntu:22.04:LTS: jupyter-server, Ubuntu:24.04:LTS: jupyter-server, Ubuntu:25.10: jupyter-server, Ubuntu:26.04:LTS: jupyter-server