{"id":"CVE-2026-40934","aliases":["GHSA-5mrq-x3x5-8v8f","PYSEC-2026-69"],"title":"Jupyter Server's Authentication Cookies Remain Valid After Password Reset and Server Restart","summary":"Jupyter Server's Authentication Cookies Remain Valid After Password Reset and Server Restart","severity":"medium","cvss":6.8,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N","vendor":"jupyter-server","product":"jupyter-server","ecosystem":"pip","affected":["jupyter-server < 2.18.0"],"patched":["jupyter-server 2.18.0"],"published":"2026-05-05","updated":"2026-09-10","sourceUpdated":"2026-09-10T03:50:45.692059585Z","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-5mrq-x3x5-8v8f","references":[{"url":"https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-5mrq-x3x5-8v8f"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-40934"},{"url":"https://github.com/jupyter-server/jupyter_server"},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/jupyter-server/PYSEC-2026-69.yaml"}],"tags":["osv","pip"],"epss":0.00308,"epssPercentile":0.23776,"ingestedAt":"2026-09-12T03:13:01.661Z","slug":"CVE-2026-40934","body":"## Overview\n\n## Summary\n\nA persistent cookie secret vulnerability allows authenticated users to maintain indefinite access even after password changes. \n\nThe 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.\n\n## PoC\n\n- Start a Jupyter server with password authentication: `jupyter server password`, `jupyter server`\n- Log in with the password and capture the authentication cookie (e.g., just login with a browser).\n- Change the password to revoke access: `jupyter server password`\n- Restart the server\n- Use the old stolen cookie => remains valid and provides full authenticated access.\n\n## Impact\n\n- All jupyter-server deployments using password authentication where security incidents may occur\n- Multi-user systems where one user's compromised session should be revocable by administrators\n- Shared or public-facing Jupyter servers where credential rotation is a security requirement\n- Any deployment where password changes are expected to revoke existing sessions\n\n## Patches\n\nJupyter Server 2.18+\n\n## Workaround\n\n```bash\nrm ~/.local/share/jupyter/runtime/jupyter_cookie_secret\n# Then restart the server\n```\n\n## Affected packages\n\n- `jupyter-server < 2.18.0`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `jupyter-server 2.18.0`","depth":"sunlit","depthScore":37,"depthScoreParts":{"impact":37.4,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}