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CVE-2026-86258

5.9 · MEDIUM

nbviewer through 1.0.1 contains a path traversal vulnerability in LocalFileHandler.can_show() that uses string-prefix comparison instead of proper path validation.

Published Sep 6, 2026CWE-22EPSS 0.52%

Overview

CVE-2026-86258 is a medium-severity vulnerability. It was published on September 6, 2026 and has a CVSS 3.1 base score of 5.9 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 5.9, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/jupyter/nbviewerGitHubgithub.com/jupyter/nbviewer/blob/1.0.1/nbviewer/providers/local/handlers.py#L92-L107GitHubgithub.com/jupyter/nbviewer/commit/aad36106f72a1ca7721310c6fccc677ce4c744a5GitHubgithub.com/jupyter/nbviewer/issues/1115Refwww.vulncheck.com/advisories/nbviewer-through-1.0.1-path-traversal-via-localfilehandler

How CyberStrike helps

Frequently asked questions

What is CVE-2026-86258?

CVE-2026-86258 is a medium-severity vulnerability. It was published on September 6, 2026 and has a CVSS 3.1 base score of 5.9 (MEDIUM).

How severe is CVE-2026-86258?

This vulnerability has a CVSS 3.1 base score of 5.9, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-86258?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-86258?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-86258 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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