What’s Vulnerable › Vulnerabilities

CVE-2026-86258: nbviewer through 1.0.1 Path Traversal via LocalFileHandler

• Severity: medium (CVSS 5.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-06 · updated 2026-09-10
• Weakness: CWE-22

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.

Affected products

• jupyter nbviewer: through 1.0.1

References

• https://github.com/jupyter/nbviewer
• https://github.com/jupyter/nbviewer/blob/1.0.1/nbviewer/providers/local/handlers.py#L92-L107
• https://github.com/jupyter/nbviewer/commit/aad36106f72a1ca7721310c6fccc677ce4c744a5
• https://github.com/jupyter/nbviewer/issues/1115
• https://www.vulncheck.com/advisories/nbviewer-through-1.0.1-path-traversal-via-localfilehandler

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