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
- 6.5.3-3, 6.5.3-4, 6.5.3-5, 7.16.4-1, 7.16.4-2, 7.16.5-1, 7.16.6-1, 7.16.6-1+deb13u1, 7.17.0-1, 7.17.1-1, 7.17.1-2
- Fixed versions
- Not specified
- CVEs
- CVE-2026-6658
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 12:18 UTC · Revision 2
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:DEBIAN-CVE-2026-6658
nbconvert
Fixed versions: Not specified
nbconvert
Fixed versions: Not specified
nbconvert
Fixed versions: Not specified
Complete source record
{
"id": "2bbb1b5842646e218c853e91cfd1a930b627829bc03a9b5f0d65b4dd37f45e41",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-6658",
"method": "structured",
"payload": {
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"title": "DEBIAN-CVE-2026-6658",
"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.",
"evidence": "osv:DEBIAN-CVE-2026-6658",
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],
"modified": "2026-10-26T11:47:27.410170215Z",
"provider": "osv",
"upstream": [
"CVE-2026-6658"
],
"references": [
"https://security-tracker.debian.org/tracker/CVE-2026-6658"
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"evidence": "/upstream"
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"security_relevant": true,
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},
"source_id": "core-osv",
"document_id": 450827,
"published_at": "2026-06-26T10:16:22.81+00:00"
}