Summary
nbconvert: Arbitrary file write through path traversal in cell output filenames when exporting to md, latex, rst and asciidoc
nbconvert <= v7.17.1 has an arbitrary file write vulnerability due to a path traversal in ipynb cell output metadata, more specifically on the filename attribute.
Vulnerable converters : --to markdown, --to latex, --to rst, --to asciidoc.
In ExtractOutputPreprocessor, extractoutput.py:116-119 joins attacker-controlled path to output_files_dir with no canonicalization check, enabling arbitrary file write.
This is a sibling vulnerability of https://github.com/advisories/GHSA-4c99-qj7h-p3vg.
PoC
In a ipynb file:
"cells": [{
"cell_type": "code", "id": "abc123", "execution_count": 1,
"metadata": {}, "source": "# PoC",
"outputs": [{
"output_type": "display_data",
"metadata": {
"filename": "../../../tmp/PWNED.png" # ← traverses outside output_dir
},
"data": {
# minimal valid PNG (1×1 pixel)
"image/png": "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNk+M9QDwADhgGAWjR9awAAAABJRU5ErkJggg=="
}
}]
}]
Impact
If a victim runs nbconvert on a malicious ipynb file, it can create some files with arbitrary data in arbitrary locations, i.e. override authorized_keys.
Note that running the cell with jupyter overrides the output, so it would "clean up" malicious cells.
Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Fixed in
Frequently Asked Questions
- What is CVE-2026-114140? CVE-2026-114140 is a high-severity path traversal vulnerability in nbconvert (pip), affecting versions >= 5.4.0, <= 7.17.1. It is fixed in 7.17.2. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
- Which versions of nbconvert are affected by CVE-2026-114140? nbconvert (pip) versions >= 5.4.0, <= 7.17.1 is affected.
- Is there a fix for CVE-2026-114140? Yes. CVE-2026-114140 is fixed in 7.17.2. Upgrade to this version or later.
- Is CVE-2026-114140 exploitable, and should I be worried? Whether CVE-2026-114140 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-114140 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-114140? Upgrade
nbconvertto 7.17.2 or later.