HighCVE-2026-66881

    Path traversal in imported file_entries name allows arbitrary file write via URL-type entry download (CVE-2026-66881)

    Published Last modified Sources: CVE.org, OSV

    Share

    What is affected, what to do

    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.

    An exploit is publicly available. Update Livebook to version 0.18.7, Livebook to version 0.19.9, Livebook to version 0.18.7-cuda12.

    Affected
    • Livebook lt 0.11.0..0.18.7
    • Livebook lt 0.19.0..0.19.9
    • Livebook lt 0.11.0-cuda12..0.18.7-cuda12
    • Livebook lt 0.19.0-cuda12..0.19.9-cuda12
    Fixed in
    • Livebook 0.18.7
    • Livebook 0.19.9
    • Livebook 0.18.7-cuda12
    • Livebook 0.19.9-cuda12

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    8.1

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    8.1

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: CVE.org, OSV

    0.6 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 49.2

    Show all metrics
    Severity
    High
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    81.90 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    PoC (publicly reported)
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    8.1 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    8.1
    CVSS v4

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    7.0
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    0.6 %
    Low — model estimates < 1% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    49.2
    High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published
    CISA assessment (SSVC)
    Exploitation: proof of concept · not automatable · Technical impact: partial
    Source: CISA Vulnrichment, as of 6 August 2026
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-23

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    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.

    Source: cvelistv5, NVD (NIST), OSV (Open Source Vulnerabilities)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    livebook-devlivebook
    • 0.19.0-cuda12 – < 0.19.9-cuda12
    • 0.11.0 – < 0.18.7
    • 0.11.0-cuda12 – < 0.18.7-cuda12
    • 0.19.0 – < 0.19.9
    • 0.19.9-cuda12
    • 0.18.7
    • 0.18.7-cuda12
    • 0.19.9
    livebooklivebook
    • 0.11.0 – < 0.18.7
    • 0.19.0 – < 0.19.9
    • 0.18.7
    • 0.19.9
    hexlivebook
    • 0.17.0
    • 0.19.1
    • 0.17.1
    • 0.15.1
    • 0.18.3
    • 0.18.4
    • 0.18.5
    • 0.16.1
    • 0.13.1
    • 0.11.0
    • 0.19.4
    • 0.15.4
    • 0.11.1
    • 0.13.2
    • 0.16.2
    • 0.18.2
    • 0.19.0
    • 0.14.0-rc.0
    • 0.14.6
    • 0.19.6
    • 0.15.5
    • 0.14.4
    • 0.13.3
    • 0.15.3
    • 0.16.3
    • 0.16.4
    • 0.17.3
    • 0.15.2
    • 0.11.4
    • 0.16.0
    • 0.12.0
    • 0.14.7
    • 0.14.0
    • 0.13.0
    • 0.14.2
    • 0.18.6
    • 0.14.0-rc.1
    • 0.18.0
    • 0.14.3
    • 0.19.5
    • 0.18.1
    • 0.11.3
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-23Relative Path Traversal

      Base

      The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize sequences such as ".." that can resolve to a location that is outside of that directory.

      Entry at MITRE CWE-23

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    Reference tagged as exploitgithub.com (opens in a new tab)PoC (publicly reported)reported, not verified—

    References & sources

    • github.comlivebook-dev/livebook/security/advisories/GHSA-r4h8-2xpq-v48gadvisory, Vendor advisory, related, Exploit, Patch, Vendor advisory
    • cna.erlef.orgcves/CVE-2026-66881.htmlweb, related, Vendor advisory
    • github.comlivebook-dev/livebook/commit/1443dd23df6e7b9203b6797f0695a807ae…fix, Patch, Patch
    • github.comlivebook-dev/livebook/commit/acf4cb8c0c79b89c795b180f061be7de2d…fix, Patch, Patch
    • github.comlivebook-dev/livebook/commit/50f86982ebf36c22abeb379b55ec0f2859…fix, Patch, Patch
    • hex.pmpackages/livebookpackage
    • OSV (Open Source Vulnerabilities)vulnerability/EEF-CVE-2026-66881related, Third-party advisory

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Initial analysis by NVDNVD

      Newly listed as affected:
      • Livebook (0.19.0 – before 0.19.9; 0.11.0 – before 0.18.7)

      CVSS V3.1: AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H

      Show 9 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      CVSSadded
      —
      AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H
      Product configurationadded
      —
      OR *cpe:2.3:a:livebook:livebook:*:*:*:*:*:*:*:* versions from (including) 0.19.0 up to (excluding) 0.19.9 *cpe:2.3:a:livebook:livebook:*:*:*:*:*:*:*:* versions from (including) 0.11.0 up to (excluding) 0.18.7
      Reference typeadded
      —
      CISA-ADP: https://github.com/livebook-dev/livebook/security/advisories/GHSA-r4h8-2xpq-v48g Types: Exploit, Patch, Vendor Advisory
      Reference typeadded
      —
      EEF: https://cna.erlef.org/cves/CVE-2026-66881.html Types: Vendor Advisory
      Reference typeadded
      —
      EEF: https://github.com/livebook-dev/livebook/commit/1443dd23df6e7b9203b6797f0695a807aeb81dde Types: Patch
      Reference typeadded
      —
      EEF: https://github.com/livebook-dev/livebook/commit/50f86982ebf36c22abeb379b55ec0f2859c83bb9 Types: Patch
      Reference typeadded
      —
      EEF: https://github.com/livebook-dev/livebook/commit/acf4cb8c0c79b89c795b180f061be7de2d8b5aa9 Types: Patch
      Reference typeadded
      —
      EEF: https://github.com/livebook-dev/livebook/security/advisories/GHSA-r4h8-2xpq-v48g Types: Exploit, Patch, Vendor Advisory
      Reference typeadded
      —
      EEF: https://osv.dev/vulnerability/EEF-CVE-2026-66881 Types: Third Party Advisory

      Source identifier: nvd@nist.gov

    2. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: proof of concept, automatable: no

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://github.com/livebook-dev/livebook/security/advisories/GHSA-r4h8-2xpq-v48g
      SSVC assessmentadded
      —
      {"id":"CVE-2026-66881","role":"CISA Coordinator","options":[{"exploitation":"poc"},{"automatable":"no"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-08-06T13:03:23.099180Z"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    3. ReceivedEEF

      CVSS V4.0: AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N

      Weakness type: CWE-23

      Description added or changed

      Show 10 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      livebook, livebook, livebook
      Descriptionadded
      —
      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.
      CVSSadded
      —
      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
      Weakness type (CWE)added
      —
      CWE-23
      Referenceadded
      —
      https://cna.erlef.org/cves/CVE-2026-66881.html
      Referenceadded
      —
      https://github.com/livebook-dev/livebook/commit/1443dd23df6e7b9203b6797f0695a807aeb81dde
      Referenceadded
      —
      https://github.com/livebook-dev/livebook/commit/50f86982ebf36c22abeb379b55ec0f2859c83bb9
      Referenceadded
      —
      https://github.com/livebook-dev/livebook/commit/acf4cb8c0c79b89c795b180f061be7de2d8b5aa9
      Referenceadded
      —
      https://github.com/livebook-dev/livebook/security/advisories/GHSA-r4h8-2xpq-v48g
      Referenceadded
      —
      https://osv.dev/vulnerability/EEF-CVE-2026-66881

      Source identifier: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db

    2 NVD translations into other languages are hidden.

    Embed badge

    Show the severity and KEV status of this vulnerability on your site – with a link back here. The image is updated hourly.

    Badge preview for CVE-2026-66881
    <a href="https://intel.neosec.eu/en/cve/CVE-2026-66881"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-66881.svg?lang=en" alt="CVE-2026-66881 – NEOSEC Intel" height="20"></a>