Jupyter nbviewer up to 1.0.1 LocalFileHandler LocalFileHandler.can_show path traversal

Summaryinfo

A vulnerability described as problematic has been identified in Jupyter nbviewer up to 1.0.1. Affected by this vulnerability is the function LocalFileHandler.can_show of the component LocalFileHandler. The manipulation results in path traversal. This vulnerability is reported as CVE-2026-86258. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Jupyter nbviewer up to 1.0.1. Affected is the function LocalFileHandler.can_show of the component LocalFileHandler. The manipulation with an unknown input leads to a path traversal vulnerability. CWE is classifying the issue as 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. This is going to have an impact on confidentiality. CVE summarizes:

nbviewer through 1.0.1 contains a path traversal vulnerability in LocalFileHandler.can_show() that uses string-prefix comparison instead of proper path validation. Attackers can read files from sibling directories outside the configured root by requesting paths that share the root as a textual prefix, disclosing unintended notebooks and credentials.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-86258 since 09/06/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 09/06/2026). The MITRE ATT&CK project declares the attack technique as T1006.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-72125). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Vendor

• Jupyter

Name

• nbviewer

Version

• 1.0.0
• 1.0.1

Website

• Product: https://github.com/jupyter/nbviewer/

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

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