jupyter-server jupyter_server up to 2.17.x REST API /api/contents path traversal

Summaryinfo

A vulnerability described as critical has been identified in jupyter-server jupyter_server up to 2.17.x. Affected by this vulnerability is an unknown functionality of the file /api/contents of the component REST API. Executing a manipulation can lead to path traversal. This vulnerability is registered as CVE-2026-35397. It is possible to launch the attack remotely. No exploit is available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in jupyter-server jupyter_server up to 2.17.x. It has been declared as critical. This vulnerability affects an unknown code block of the file /api/contents of the component REST API. The manipulation with an unknown input leads to a path traversal vulnerability. The CWE definition for the vulnerability is CWE-22. The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

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 names do not share a common prefix with any sibling directory.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-35397 since 04/02/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1006.

Upgrading to version 2.18.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-27470). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Vendor

• jupyter-server

Name

• jupyter_server

Version

• 2.0
• 2.1
• 2.2
• 2.3
• 2.4
• 2.5
• 2.6
• 2.7
• 2.8
• 2.9
• 2.10
• 2.11
• 2.12
• 2.13
• 2.14
• 2.15
• 2.16
• 2.17

Website

• Product: https://github.com/jupyter-server/jupyter_server/

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VulDB is the best source for vulnerability data and more expert information about this specific topic.

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