Bug 2459952 (CVE-2026-39378)

Summary: CVE-2026-39378 nbconvert: nbconvert: Sensitive file exfiltration via path traversal in image references
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: anthomas, ehelms, ggainey, jkoehler, juwatts, lphiri, mhulan, nmoumoul, osousa, pcreech, rchan, rjohnson, smallamp, tmalecek
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in nbconvert, a tool used to convert Jupyter notebooks. A malicious notebook can exploit this vulnerability when the `HTMLExporter.embed_images` setting is enabled. This allows for path traversal in image references, which can lead to arbitrary file read. Consequently, sensitive files from the conversion host could be exposed by embedding them as base64 data in the output HTML.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Description OSIDB Bzimport 2026-04-21 02:01:59 UTC
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.