---
id: CVE-2026-86258
title: >-
  nbviewer through 1.0.1 contains a path traversal vulnerability in
  LocalFileHandler.can_show() that uses string-prefix comparison instead of
  proper path validation
summary: >-
  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 …
severity: medium
cvss: 5.9
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N'
cwe:
  - CWE-22
vendor: jupyter
product: nbviewer
affected:
  - nbviewer <= 1.0.1
published: '2026-09-06'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T16:18:02.407'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-86258'
references:
  - url: 'https://github.com/jupyter/nbviewer'
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/jupyter/nbviewer/blob/1.0.1/nbviewer/providers/local/handlers.py#L92-L107
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/jupyter/nbviewer/commit/aad36106f72a1ca7721310c6fccc677ce4c744a5
    label: disclosure@vulncheck.com
  - url: 'https://github.com/jupyter/nbviewer/issues/1115'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/nbviewer-through-1.0.1-path-traversal-via-localfilehandler
    label: disclosure@vulncheck.com
tags:
  - nvd
  - cve.org
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-10T14:19:03.319609Z'
epss: 0.00363
epssPercentile: 0.30141
ingestedAt: '2026-09-07T05:05:30.497Z'
---

## Overview

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

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.