Bug 2558555 (CVE-2026-114140)

Summary: CVE-2026-114140 nbconvert: nbconvert: arbitrary file write via path traversal in ExtractOutputPreprocessor
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in nbconvert. This flaw allows an attacker to perform an arbitrary file write by enticing a user to convert a maliciously crafted Jupyter notebook. Due to improper path validation in ExtractOutputPreprocessor, attacker-controlled cell output metadata can traverse outside the target directory, allowing arbitrary files to be created or overwritten with the user's privileges.
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Description OSIDB Bzimport 2026-10-21 20:32:48 UTC 
The nbconvert tool, jupyter nbconvert, converts Jupyter notebooks to various other formats via Jinja templates. From 5.4.0 until 7.17.2, ExtractOutputPreprocessor in nbconvert/preprocessors/extractoutput.py joins the attacker-controlled cell output metadata filename to output_files_dir without limiting the result to the intended directory. When a victim converts a malicious notebook with the markdown, LaTeX, reStructuredText, or AsciiDoc exporter, path traversal in the output filename can write attacker-controlled output data to arbitrary locations accessible to the victim. Running the notebook cell again replaces the malicious output metadata, but merely converting the supplied notebook does not. This issue is fixed in version 7.17.2.