CVE-2026-86258

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.

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