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Vulnerability record · CVE-2026-86258 · published 6 September 2026

CVE-2026-86258: Path traversal vulnerability

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.

8.2 CVSS 4.0 High EPSS 0.52% · top 58.0% CWE-22 · Path traversal Awaiting Analysis
8.2CVSS 4.0 base score
0.52%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
5References
10 Sep 2026Last modified by NVD

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:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
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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Source: NIST National Vulnerability Database (record CVE-2026-86258), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.