Reference page — cumulative record through Thursday, August 20, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.
CVE-2026-66881
livebook-dev livebook — Path traversal in imported file_entries name allows arbitrary file write via URL-type entry download
AV AC AT PR UI VC VI VA CVSS EPSS %ile KEV
N L N N A N H L 7.0 .0038 31.0 —
AFFECTED
Product Versions Fixed
livebook 0.11.0 – —
livebook 0.11.0 – —
livebook c02eb984f80a543c7a52b1d882c76f56aa5be743 – 1443dd23df6e7b9203b6797f0695a807aeb81dde
TIMELINE
Jul 28 Reserved by EEF
Aug 5 EXPLOIT PUBLISHED — CVE-2026-66881 (livebook-dev livebook). Public exploit reference added.
Aug 5 Published (CNA: EEF)
Aug 10 EXPLOIT PUBLISHED — CVE-2026-66881 (livebook-dev livebook). Public exploit reference added.
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 filesystem root. When the entry's content is requested and no cached copy exists, Livebook fetches the entry's URL and writes the response body to the resolved path, creating parent directories as needed. The attacker therefore controls both the destination and the contents of the written file, which may land anywhere the Livebook process can write. The same missing containment check is present in Livebook.Session.to_attachment_file_entry/2.
A victim who opens an attacker-supplied notebook and causes the entry to be fetched triggers the write within their own authenticated session; the attacker needs no account on the target instance. URL-type entries are also not placed under notebook stamping quarantine on import, so no warning is shown.
This issue affects livebook: from 0.11.0 before 0.18.7 and from 0.19.0 before 0.19.9.
Lifecycle
Complete event history — 4 events, chronological
| Date | Event | Detail |
|---|
| July 28, 2026 | Reserved | Reserved by EEF |
| August 5, 2026 | EXPLOIT PUBLISHED | EXPLOIT PUBLISHED — CVE-2026-66881 (livebook-dev livebook). Public exploit reference added. |
| August 5, 2026 | Published | Published (CNA: EEF) |
| August 10, 2026 | EXPLOIT PUBLISHED | EXPLOIT PUBLISHED — CVE-2026-66881 (livebook-dev livebook). Public exploit reference added. |
Affected
Affected products and packages — 3 rows
| Vendor | Product / Package | Ecosystem | Version introduced | Fixed |
|---|
| livebook-dev | livebook | — | 0.11.0 | — |
| livebook-dev | livebook | — | 0.11.0 | — |
| livebook-dev | livebook | — | c02eb984f80a543c7a52b1d882c76f56aa5be743 | 1443dd23df6e7b9203b6797f0695a807aeb81dde |
About this page
This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-66881 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Thursday, August 20, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.