CVE-2026-66881

Technical Description

Relative Path Traversal vulnerability in livebook-dev livebook allows an attacker-authored notebook to write a file with attacker-controlled content to an arbitrary path.

A .livemd notebook can declare file_entries metadata, each entry carrying a name. Every path that creates a file entry through the user interface validates that name with Livebook.Notebook.validate_file_entry_name/2, which requires a flat filename of alphanumerics, dashes, underscores and dots, ending in an extension. The import path does not: Livebook.LiveMarkdown.Import.file_entry_metadata_to_attrs/1 in lib/livebook/live_markdown/import.ex takes the name verbatim from the notebook source.

For a URL-type file entry, Livebook.Session.file_entry_cache_file/2 in lib/livebook/session.ex resolves that name beneath the session's temporary directory without checking that the result stays inside it, and Livebook.FileSystem.Utils.resolve_unix_like_path/2 collapses parent-directory segments while clamping only at the filesys

Remediation

Check the references section for vendor advisories and patches from livebook. Update livebook to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected Products

References