Path Traversal in Jupyter Nbviewer
CVE-2026-86258
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.
Vulnerability class: Path Traversal (Directory Traversal)
CVSS v3 metric
CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N.
Affected products
Weakness classification (CWE)
References
- disclosure@vulncheck.com (issue-tracking)
- disclosure@vulncheck.com (technical-description)
- disclosure@vulncheck.com (patch)
- disclosure@vulncheck.com (product)
- disclosure@vulncheck.com (third-party-advisory)
Frequently asked questions
- What is CVE-2026-86258?
- CVE-2026-86258 is a medium-severity vulnerability in Jupyter Nbviewer, classified under Path Traversal. CVSS score: 5.9/10. Published 2026-09-06.
- How severe is CVE-2026-86258?
- Medium severity. CVSS v3 base score is 5.9 out of 10.