Medium severity · published Sep 6, 2026
CVE-2026-86258
nbviewer through 1.0.1 Path Traversal via LocalFileHandler
5.9
CVSS
0.5%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Confidentiality
High
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 44% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
NB
nbviewer · jupyter
through 1.0.1 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-86258
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-86258
github.com
https://github.com/jupyter/nbviewer
github.com
https://github.com/jupyter/nbviewer/blob/1.0.1/nbviewer/providers/local/handlers.py#L92-L107
github.com
https://github.com/jupyter/nbviewer/commit/aad36106f72a1ca7721310c6fccc677ce4c744a5
github.com
https://github.com/jupyter/nbviewer/issues/1115
www.vulncheck.com
https://www.vulncheck.com/advisories/nbviewer-through-1.0.1-path-traversal-via-localfilehandler