Jupyter Server vulnerable to Path Traversal via incorrect root directory boundary check in _get_os_path()

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.8 · CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

EPSS

• CVE-2026-5422: 4.86% estimated exploitation activity in the next 30 days; percentile 92.05 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

A path traversal vulnerability exists in jupyter-server version 2.17.0 due to an incorrect root directory boundary check in the _get_os_path() function within jupyter_server/services/contents/fileio.py. The check uses startswith(root) without appending a trailing path separator, allowing sibling directories with names starting with the same prefix as root_dir to bypass the check. Additionally, the to_os_path() function in utils.py does not strip ".." from path parts, enabling traversal sequences to bypass the vulnerable check. This vulnerability can lead to unauthorized read/write access to files in sibling directories, potentially exposing sensitive data in shared hosting environments.

Published by the source

13 Jul 2026, 15:46 UTC

Last modified by the source

13 Jul 2026, 16:31 UTC

Source last checked

24 Oct 2026, 04:13 UTC

1. Revision 1 · created · 24 Oct 2026

   Published from osv record PYSEC-2026-2532

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# Patch Next advisory brief: CVE-2026-5422

Advisory: Jupyter Server vulnerable to Path Traversal via incorrect root directory boundary check in _get_os_path()
IDs: CVE-2026-5422, GHSA-gf7q-q4j7-hp7c
Record: https://patchnext.com/advisories/cve-2026-5422 (revision 1, source checked 24 Oct 2026, 04:13 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: jupyter-server 2.18.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI jupyter-server: affected < 2.18.2; fixed in 2.18.2

## Suggested inspection (read-only)
- `python -m pip show jupyter-server`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on jupyter-server.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/PYSEC-2026-2532 (OSV record PYSEC-2026-2532 lists affected ranges: PyPI jupyter-server >=0 <2.18.2 (fixed))

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