CVE-2026-66881

Name of the Vulnerable Software and Affected Versions livebook versions 0.11.0 through 0.18.6 livebook versions 0.19.0 through 0.19.8

Description A Relative Path Traversal issue allows an attacker to write a file with controlled content to an arbitrary path on the system. This occurs because the import path in Livebook.LiveMarkdown.Import.file entry metadata to attrs/1 takes the name from the notebook source verbatim without validation. For URL-type file entries, the function Livebook.Session.file entry cache file/2 resolves the name beneath the session temporary directory without verifying if the result remains within that directory. Additionally, Livebook.FileSystem.Utils.resolve unix like path/2 collapses parent-directory segments but only clamps at the filesystem root. Consequently, when content is requested and no cache exists, the system writes the response body to the resolved path, creating parent directories as needed. This allows an attacker to control both the destination and content of the written file anywhere the process has write permissions. A similar lack of containment check exists in Livebook.Session.to attachment file entry/2. A victim triggers this by opening an attacker-supplied notebook and causing the entry to be fetched within their authenticated session.

Recommendations Update livebook versions 0.11.0 through 0.18.6 to version 0.18.7. Update livebook versions 0.19.0 through 0.19.8 to version 0.19.9.