How severe is CVE-2026-39378?

CVE-2026-39378 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2026-39378 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (23rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-39378?

CVE-2026-39378 affects Jupyter Nbconvert. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-39378?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-39378 have an EU (EUVD) identifier?

Yes. CVE-2026-39378 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-24025.

When was CVE-2026-39378 published?

CVE-2026-39378 was published on 2026-04-21 and last updated on 2026-06-17.

CVE-2026-39378

CVE-2026-39378 is a medium-severity vulnerability in Jupyter Nbconvert with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-22.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
EPSS exploit prediction: 0% (23rd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-24025
Weakness: CWE-22
Affected product: Jupyter Nbconvert
Published: 2026-04-21
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-39378?: 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.
How severe is CVE-2026-39378?: CVE-2026-39378 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2026-39378 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (23rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-39378?: CVE-2026-39378 affects Jupyter Nbconvert. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-39378?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-39378 have an EU (EUVD) identifier?: Yes. CVE-2026-39378 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-24025.
When was CVE-2026-39378 published?: CVE-2026-39378 was published on 2026-04-21 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:jupyter:nbconvert:*:*:*:*:*:python:*:*

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