CVE-2026-6658
Cross-site Scripting (XSS) in jupyter/nbconvert
Description
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 `<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.
INFO
Published Date :
June 26, 2026, 10:16 a.m.
Last Modified :
June 26, 2026, 8:08 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.0 | MEDIUM | MITRE-CVE | ||||
| CVSS 3.0 | MEDIUM | [email protected] |
Solution
- Update jupyter/nbconvert to a patched version.
- Ensure mermaid output is properly sanitized.
- Review security configurations for HTML exports.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-6658.
| URL | Resource |
|---|---|
| https://huntr.com/bounties/47570290-3b26-4477-8cfa-fdef7db5aefe | |
| https://huntr.com/bounties/47570290-3b26-4477-8cfa-fdef7db5aefe |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-6658 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-6658
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-6658 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-6658 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 26, 2026
Action Type Old Value New Value Added Reference https://huntr.com/bounties/47570290-3b26-4477-8cfa-fdef7db5aefe Added SSVC {'id': 'CVE-2026-6658', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-06-26T10:19:03.505659Z'} -
New CVE Received by [email protected]
Jun. 26, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'jupyter', 'product': 'jupyter/jupyter', 'versions': [{'status': 'affected', 'version': 'unspecified', 'versionType': 'custom', 'lessThanOrEqual': 'latest'}]}] Added Description 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 `<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. Added CVSS V3 AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N Added CWE CWE-79 Added Reference https://huntr.com/bounties/47570290-3b26-4477-8cfa-fdef7db5aefe