Relative Path Traversal vulnerability in livebook-dev livebook allows an attacker-authored notebook to write a file with…
CVE-2026-66881
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 fileentries metadata, each entry carrying a name. Every path that creates a file entry through the user interface validates that name with Livebook.Notebook.validatefileentryname/2, which requires a flat filename of alphanumerics, dashes, underscores and dots, ending in an extension. The import path does not: Livebook.LiveMarkdown.Import.fileentrymetadatatoattrs/1 in lib/livebook/livemarkdown/import.ex takes the name verbatim from the notebook source. For a URL-type file entry, Livebook.Session.fileentrycachefile/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.resolveunixlikepath/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…
Assessment
- CVSS
- 7 (v4.0)
- Severity
- High
- EPSS
- 0.61% chance of exploitation in the next 30 days
- Known exploited
- Not listed in CISA KEV
- Exploit availability
- Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
- Published
- 5 August 2026
- Last updated
- 10 November 2026
- Affected
- livebook-dev · livebook
- Assigner
- EEF
CVSS vectorCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N
At the source
References
- https://github.com/livebook-dev/livebook/security/advisories/GHSA-r4h8-2xpq-v48g
- https://cna.erlef.org/cves/CVE-2026-66881.html
- https://osv.dev/vulnerability/EEF-CVE-2026-66881
- https://github.com/livebook-dev/livebook/commit/c02eb984f80a543c7a52b1d882c76f56aa5be743
- https://github.com/livebook-dev/livebook/commit/1443dd23df6e7b9203b6797f0695a807aeb81dde
- https://github.com/livebook-dev/livebook/commit/acf4cb8c0c79b89c795b180f061be7de2d8b5aa9
- https://github.com/livebook-dev/livebook/commit/50f86982ebf36c22abeb379b55ec0f2859c83bb9
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