dbcve.org
NbconvertApplication · Jupyter

CVE-2026-39378

MEDIUM · 6.5 CVSS v3.1 Published 2026-04-21
Fix available
A fix is available. Upgrade to 7.17.1 or later.
See remediation →
72/100
Remediation priority · Elevated
Remotely reachable No privileges

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
The nbconvert tool, jupyter nbconvert, converts Jupyter notebooks to various other formats via Jinja templates. In versions 6.5 through 7.17.0, 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. nbconvert 7.17.1 contains a fix. As a workaround, do not enable `HTMLExporter.embed_images`; it is not enabled by default.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A path traversal vulnerability in nbconvert's markdown renderer allows arbitrary file read when HTMLExporter.embed_images is enabled. A malicious notebook can embed sensitive files from the conversion host as base64 data URIs in the output HTML.

MitigationUpgrade nbconvert to version 7.17.1 or later. As a workaround, ensure HTMLExporter.embed_images is not enabled in notebook conversion configurations.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
NbconvertApplication
Affected:>= 6.5.0, < 7.17.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check installed nbconvert version
    Run `pip show nbconvert` or `pip freeze | grep nbconvert` to get the installed version number
    Affected if Version is >= 6.5.0 and < 7.17.1
  2. Locate nbconvert configuration files
    Check for config files in the conversion environment: `~/.jupyter/jupyter_nbconvert_config.py`, `<notebook_dir>/.jupyter/jupyter_nbconvert_config.py`, or any custom config passed via `--config`
    Affected if Configuration file exists and contains `HTMLExporter(embed_images=True)` or `c.HTMLExporter.embed_images = True`
  3. Check for embed_images in notebook metadata or conversion arguments
    Inspect notebook files for embedded image configurations, or review CI/CD/build scripts that run nbconvert for the flag `--embed-images` or `embed_images=True`
    Affected if Notebook conversion explicitly sets embed_images=True or uses the embed-images flag
  4. Check active conversion templates
    Look in `<site-packages>/nbconvert/exporters/` or custom exporter directories for any HTMLExporter subclass that hardcodes embed_images=True
    Affected if Custom exporter code or template configuration enables embedding of external files

Environment is affected if nbconvert version is in the vulnerable range AND HTMLExporter.embed_images is enabled in any configuration or conversion pipeline.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 7.17.1 or later
Fixed in 7.17.1
Interim mitigation

Upgrade nbconvert to version 7.17.1 or later. As a workaround, ensure HTMLExporter.embed_images is not enabled in notebook conversion configurations.

Recommended fix High confidence

7.17.1 or later

  1. Upgrade nbconvert to version 7.17.1 or later using your package manager (e.g., pip install --upgrade nbconvert>=7.17.1)
  2. Verify the upgrade was successful by running nbconvert --version
  3. As an alternative mitigation if immediate upgrade is not feasible, ensure HTMLExporter.embed_images is not enabled in your conversion settings (it is disabled by default)

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Nbconvert Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing3.0 h
  • Review / QA2.0 h
8.0 hours of engineering $1,390
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-39378 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data