Medium
nbconvert — security advisory
A 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 `` 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.
- Products
- nbconvert
- Affected versions
- 4.2.0-4, 5.3.1-1, 5.4-2ubuntu2, 5.6.0-1, 5.6.0-2, 5.6.1-1, 5.6.1-3, 6.1.0-1, 6.3.0-1, 6.4.0-1, 6.5.3-4, 6.5.3-5, 7.16.6-1, 7.17.0-1, 7.17.1-2
- Fixed versions
- Not specified
- CVEs
- CVE-2026-6658
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 03:13 UTC · Revision 1
Source evidence
A 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 `` 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.
osv:UBUNTU-CVE-2026-6658
nbconvert
Fixed versions: Not specified
nbconvert
Fixed versions: Not specified
nbconvert
Fixed versions: Not specified
nbconvert
Fixed versions: Not specified
nbconvert
Fixed versions: Not specified
nbconvert
Fixed versions: Not specified
nbconvert
Fixed versions: Not specified
Complete source record
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"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-6658",
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"summary": "A 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 `` 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.",
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"modified": "2026-10-17T13:00:35.171682108Z",
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"references": [
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