How severe is CVE-2026-39377?

CVE-2026-39377 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 none, integrity high, and availability none.

Is CVE-2026-39377 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (18th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-39377?

CVE-2026-39377 affects Jupyter Nbconvert. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-39377?

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

Does CVE-2026-39377 have an EU (EUVD) identifier?

Yes. CVE-2026-39377 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-24023.

When was CVE-2026-39377 published?

CVE-2026-39377 was published on 2026-04-21 and last updated on 2026-06-17.

CVE-2026-39377

CVE-2026-39377 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% (18th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-24023
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. Versions 6.5 through 7.17.0 allow arbitrary file writes to locations outside the intended output directory when processing notebooks containing crafted cell attachment filenames. The `ExtractAttachmentsPreprocessor` passes attachment filenames directly to the filesystem without sanitization, enabling path traversal attacks. This vulnerability provides complete control over both the destination path and file extension. Version 7.17.1 contains a patch.

Frequently asked questions

What is CVE-2026-39377?: The nbconvert tool, jupyter nbconvert, converts Jupyter notebooks to various other formats via Jinja templates. Versions 6.5 through 7.17.0 allow arbitrary file writes to locations outside the intended output directory when processing notebooks containing crafted cell attachment filenames. The `ExtractAttachmentsPreprocessor` passes attachment filenames directly to the filesystem without sanitization, enabling path traversal attacks. This vulnerability provides complete control over both the destination path and file extension. Version 7.17.1 contains a patch.
How severe is CVE-2026-39377?: CVE-2026-39377 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 none, integrity high, and availability none.
Is CVE-2026-39377 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (18th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-39377?: CVE-2026-39377 affects Jupyter Nbconvert. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-39377?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-39377 have an EU (EUVD) identifier?: Yes. CVE-2026-39377 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-24023.
When was CVE-2026-39377 published?: CVE-2026-39377 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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