Medium severity · published Apr 21, 2026
CVE-2026-39377
nbconvert has an Arbitrary File Write via Path Traversal in Cell Attachment Filenames
6.5
CVSS
0.3%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
None
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 18% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
NB
nbconvert · jupyter
>= 6.5, < 7.17.1 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-39377
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-39377
Product
https://github.com/jupyter/nbconvert/releases/tag/v7.17.1
Mitigation
https://github.com/jupyter/nbconvert/security/advisories/GHSA-4c99-qj7h-p3vg
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