Cross-site Scripting (XSS) in jupyter/nbconvert

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Summary

CVECVE-2026-6658
StatePUBLISHED
Assigner@huntr_ai
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-26 10:16:22 UTC
Updated2026-06-26 20:08:23 UTC
DescriptionA vulnerability in jupyter/nbconvert versions <= 7.17.0 allows for Cross-site Scripting (XSS) via unsanitized `text/vnd.mermaid` output in HTML exports. The `data_mermaid` block in `share/templates/lab/base.html.j2` renders `text/vnd.mermaid` cell output directly into HTML without escaping, enabling attackers to inject arbitrary HTML/JavaScript by breaking out of the `<pre>` tag. This vulnerability impacts any server using nbconvert to render notebooks as HTML, allowing attackers to execute arbitrary JavaScript in the context of users viewing the HTML export.

Risk And Classification

Primary CVSS: v3.0 5.4 MEDIUM from [email protected]

CVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

EPSS: 0.001340000 probability, percentile 0.032440000 (date 2026-06-29)

Problem Types: CWE-79 | CWE-79 CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

VersionSourceTypeScoreSeverityVector
3.0[email protected]Secondary5.4MEDIUMCVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
3.0CNADECLARED5.4MEDIUMCVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

CVSS v3.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Jupyter Jupyter/jupyter affected unspecified latest custom Not specified

References

ReferenceSourceLinkTags
huntr.com/bounties/47570290-3b26-4477-8cfa-fdef7db5aefe 134c704f-9b21-4f2e-91b3-4a467353bcc0 huntr.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis
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