# CVE-2026-39378: nbconvert has an Arbitrary File Read via Path Traversal in HTMLExporter Image Embedding

> Attackers can read arbitrary files from the host by exploiting path traversal in image embedding when the embed_images option is enabled.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 21 Apr 2026
- **Updated:** 21 Apr 2026
- **Also known as:** CLEANSTART-2026-RQ83656, CLEANSTART-2026-VX32079, DEBIAN-CVE-2026-39378, GHSA-7jqv-fw35-gmx9, PYSEC-2026-2230, UBUNTU-CVE-2026-39378

## What is CVE-2026-39378?

CVE-2026-39378 is a medium-severity path traversal vulnerability in jupyter nbconvert, published on 21 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

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.

Weakness: CWE-73 (External Control of File Name or Path), CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-39378?

3 open source packages ship an affected version, including nbconvert. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `nbconvert` | PyPI | From 6.5.0 | 7.17.1 |
| `nbconvert` | PyPI | From 6.5.0 | 7.17.1 |
| `nbconvert` | PyPI | From 6.5.0 | 7.17.1 |

Products: Jupyter Nbconvert.

## How do I fix CVE-2026-39378?

Upgrade nbconvert to 7.17.1 or later.

## Is CVE-2026-39378 being exploited?

There is no known exploitation of CVE-2026-39378 in the wild and no public exploit code.

## Other vulnerabilities in jupyter nbconvert

- [CVE-2025-53000](https://insights.sbomify.com/CVE-2025-53000/): nbconvert has an uncontrolled search path that leads to unauthorized code execution on Windows (high 8.5)
- [CVE-2026-39377](https://insights.sbomify.com/CVE-2026-39377/): nbconvert has an Arbitrary File Write via Path Traversal in Cell Attachment Filenames (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-39378 and fix it if it is affected.

What it is: CVE-2026-39378 is a medium-severity path traversal vulnerability in jupyter nbconvert, published on 21 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-39378 in the wild and no public exploit code.

Affected packages and fixed versions:
- nbconvert (PyPI): affected from 6.5.0; fixed in 7.17.1
- nbconvert (PyPI): affected from 6.5.0; fixed in 7.17.1
- nbconvert (PyPI): affected from 6.5.0; fixed in 7.17.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-39378/ (Markdown: https://insights.sbomify.com/CVE-2026-39378/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-39378
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-39378
- OSV: https://osv.dev/vulnerability/CVE-2026-39378

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-39378/
Summaries are generated and may contain mistakes; the official description above is the record.