Jupyter Server's Authentication Cookies Remain Valid After Password Reset and Server Restart
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
rm ~/.local/share/jupyter/runtime/jupyter_cookie_secret
# Then restart the serverAffected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | jupyter-server | < 2.18.0 | 2.18.0 |
References
- CVSS vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N- Weakness (CWE)
CWE-613- Platform
- Python (PyPI)
- Package
jupyter-server- Disclosed
- 05.05.2026
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-69 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-5mrq-x3x5-8v8f - CC BY 4.0
Vulnerability history: jupyter-server
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 14
- First → latest
- 11.2020 09.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 1
- High 7
- Medium 6
Disclosures per year
- 2020: 2
- 2021: 0
- 2022: 2
- 2023: 3
- 2024: 1
- 2025: 0
- 2026: 6
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