Path traversal in imported file_entries name allows arbitrary file write via URL-type entry download

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-66881
StatePUBLISHED
AssignerEEF
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-05 20:17:12 UTC
Updated2026-08-05 20:17:12 UTC
DescriptionRelative 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.

Risk And Classification

Primary CVSS: v4.0 7 HIGH from 6b3ad84c-e1a6-4bf7-a703-f496b71e49db

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:L/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:X/V:X/RE:X/U:X

Problem Types: CWE-23 | CWE-23 CWE-23 Relative Path Traversal

VersionSourceTypeScoreSeverityVector
4.06b3ad84c-e1a6-4bf7-a703-f496b71e49dbSecondary7HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/C...
4.0CNACVSS7HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
Active
Confidentiality
None
Integrity
High
Availability
Low
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:L/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:X/V:X/RE:X/U:X

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Livebook-dev Livebook affected 0.11.0 0.18.7 semver Not specified
CNA Livebook-dev Livebook affected 0.19.0 0.19.9 semver Not specified
CNA Livebook-dev Livebook affected 0.11.0 0.18.7 other Not specified
CNA Livebook-dev Livebook affected 0.19.0 0.19.9 other Not specified
CNA Livebook-dev Livebook affected 0.11.0-cuda12 0.18.7-cuda12 other Not specified
CNA Livebook-dev Livebook affected 0.19.0-cuda12 0.19.9-cuda12 other Not specified
CNA Livebook-dev Livebook affected c02eb984f80a543c7a52b1d882c76f56aa5be743 * git Not specified

References

ReferenceSourceLinkTags
github.com/livebook-dev/livebook/commit/1443dd23df6e7b9203b6797f0695a807... 6b3ad84c-e1a6-4bf7-a703-f496b71e49db github.com
cna.erlef.org/cves/CVE-2026-66881.html 6b3ad84c-e1a6-4bf7-a703-f496b71e49db cna.erlef.org
github.com/livebook-dev/livebook/commit/acf4cb8c0c79b89c795b180f061be7de... 6b3ad84c-e1a6-4bf7-a703-f496b71e49db github.com
github.com/livebook-dev/livebook/commit/50f86982ebf36c22abeb379b55ec0f28... 6b3ad84c-e1a6-4bf7-a703-f496b71e49db github.com
osv.dev/vulnerability/EEF-CVE-2026-66881 6b3ad84c-e1a6-4bf7-a703-f496b71e49db osv.dev
github.com/livebook-dev/livebook/security/advisories/GHSA-r4h8-2xpq-v48g 6b3ad84c-e1a6-4bf7-a703-f496b71e49db github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Nguyễn Công Tú (en)

CNA: Jonatan Männchen / EEF (en)

CNA: Jonatan Kłosko (en)

CNA: José Valim (en)

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