CVE-2026-39378: Nbconvert Path Traversal Vulnerability

MODERATE
Advisory Identifier: GHSA-7jqv-fw35-gmx9
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CVSS 6.5
CWE-23 CWE-22
Published
Advisory Summary

CVE-2026-39378 is a MODERATE (CVSS 6.5) path traversal vulnerability (CWE-23: Relative Path Traversal) affecting Nbconvert libraries in the PyPI ecosystem. The issue involves nbconvert has an arbitrary file read via path traversal in htmlexporter image embedding. Remediation is available by upgrading affected packages to version 7.17.1.

CVE-2026-39378 at a Glance

CVE Identifier CVE-2026-39378
GHSA Identifier GHSA-7jqv-fw35-gmx9
Severity MODERATE
CVSS v3.1 Base Score 6.5
CWE Classification CWE-23: Relative Path Traversal
Affected Product Nbconvert
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 6.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction Required (UI:R)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2026-39378

To remediate this vulnerability, upgrade all affected Nbconvert dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

nbconvert fixed: 7.17.1 
pip install nbconvert>=7.17.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show nbconvert

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-39378, inspect your installed packages using pip:

pip show nbconvert

Analyze the terminal output to locate any version of Nbconvert in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 7.17.1), your application is affected.

Note: The pip show nbconvert command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-23: Relative Path Traversal, where 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. In Nbconvert, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

## Summary When `HTMLExporter.embed_images=True`, nbconvert's markdown renderer allows arbitrary file read via path traversal in image references. A malicious notebook can exfiltrate sensitive files from the conversion host by embedding them as base64 data URIs in the output HTML. ## Patches Upgrade to nbconvert 7.17.1 ## Workarounds Do not enable `HTMLExporter.embed_images` (it is not enabled by default).

CVE-2026-39378 Affected Nbconvert Versions

1 component(s)
Fixed Versions:
7.17.1
Product / Package Ecosystem Affected Versions Fixed Version
nbconvert
pypi/nbconvert
PyPI
≥ 6.5.0
< 7.17.1
7.17.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/jupyter/nbconvert/security/advisories/GHSA-7jqv-fw35-gmx9
NVD — CVE-2026-39378 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-39378
Nbconvert Source Repository REPOSITORY
https://github.com/jupyter/nbconvert
Nbconvert Release RELEASE
https://github.com/jupyter/nbconvert/releases/tag/v7.17.1

Frequently Asked Questions

What is CVE-2026-39378?
CVE-2026-39378 is a security vulnerability in Nbconvert involving nbconvert has an Arbitrary File Read via Path Traversal in HTMLExporter Image Embedding under CWE-23: Relative Path Traversal.
Which Nbconvert versions are affected?
Affected versions include releases prior to 7.17.1 across affected packages: nbconvert.
What version fixes CVE-2026-39378?
Upgrading to 7.17.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is nbconvert affected?
Yes, nbconvert is affected in releases prior to 7.17.1. Upgrade your dependency to 7.17.1 or later.
What is the CVSS score of CVE-2026-39378?
CVE-2026-39378 has a CVSS v3.1 base score of 6.5 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N.
What CWE is associated with CVE-2026-39378?
CVE-2026-39378 is classified under CWE-23: Relative Path Traversal (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.).
How can I check PyPI dependencies for CVE-2026-39378?
Run the dependency tree command: 'pip show nbconvert'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-7jqv-fw35-gmx9",
  "modified" : "2026-04-21T17:18:53Z",
  "published" : "2026-04-21T17:18:53Z",
  "aliases" : [ "CVE-2026-39378" ],
  "summary" : "nbconvert has an Arbitrary File Read via Path Traversal in HTMLExporter Image Embedding",
  "details" : "## Summary\n\nWhen `HTMLExporter.embed_images=True`, nbconvert's markdown renderer allows arbitrary file read via path traversal in image references. A malicious notebook can exfiltrate sensitive files from the conversion host by embedding them as base64 data URIs in the output HTML.\n\n## Patches\n\nUpgrade to nbconvert 7.17.1\n\n## Workarounds\n\nDo not enable `HTMLExporter.embed_images` (it is not enabled by default).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "nbconvert"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "6.5.0"
      }, {
        "fixed" : "7.17.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/jupyter/nbconvert/security/advisories/GHSA-7jqv-fw35-gmx9"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-39378"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/jupyter/nbconvert"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jupyter/nbconvert/releases/tag/v7.17.1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22", "CWE-23" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-21T17:18:53Z",
    "nvd_published_at" : "2026-04-21T01:16:06Z"
  }
}