Path Traversal in Jupyter Jupyter/jupyter

CVE-2026-5422

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 · last modified .

CVSS v3 metric

CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.005 (44.8th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 45th percentile — 44.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-5422: held from 0.004 to 0.005.

EPSS over last 30 days · oldest: 0.004 · newest: 0.005 · change: +0.001

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-5422?
CVE-2026-5422 is a high-severity vulnerability in Jupyter Jupyter/jupyter, classified under Relative Path Traversal. CVSS score: 8.1/10. Published 2026-06-02.
How severe is CVE-2026-5422?
High severity. CVSS v3 base score is 8.1 out of 10.