CVE-2026-39378Network attack vector

Host file disclosure via traversing image paths

Published Apr 21, 2026 · Updated Apr 21, 2026

Path traversal in Project Jupyter nbconvert 6.5.0 through 7.17.0 allows attackers to read host files through crafted notebook images. In markdown_mistune.py, _src_to_base64 joins an image src to the notebook working path and reads it without checking that the resolved path remains within that directory. Exploitation requires a victim to convert the notebook with non-default HTMLExporter.embed_images enabled; file bytes then appear as base64 data URLs in the HTML output.

CVSS severity6.5
Medium
EPSS probability0.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path traversal in Project Jupyter nbconvert 6.5.0 through 7.17.0 allows attackers to read host files through crafted notebook images. In markdown_mistune.py, _src_to_base64 joins an image src to the notebook working path and reads it without checking that the resolved path remains within that directory. Exploitation requires a victim to convert the notebook with non-default HTMLExporter.embed_images enabled; file bytes then appear as base64 data URLs in the HTML output.

The record

CVE
CVE-2026-39378
Published
Apr 21, 2026
Updated
Apr 21, 2026
Vendor
Project Jupyter
Product
nbconvert
Classifications
CWE-22, CWE-23, T1005
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 6.5, < 7.17.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Project Jupyter · nbconvertversion=>= 6.5, < 7.17.1

Published CVSS scores

6.5GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
CWE-23Relative Path Traversal
T1005Data from Local System

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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