Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-06-26T09:40:30 nbconvert: nbconvert: Cross-site Scripting via unsanitized Mermaid output in HTML exports 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N CWE-79

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.

A flaw was found in nbconvert. This vulnerability allows a remote attacker to perform Cross-site Scripting (XSS) by injecting arbitrary HTML or JavaScript code. This occurs due to unsanitized `text/vnd.mermaid` output in HTML exports, where the `data_mermaid` block directly renders cell output without proper escaping. Successful exploitation enables attackers to execute arbitrary JavaScript in the context of users viewing the exported HTML notebooks.

This Moderate severity Cross-site Scripting (XSS) flaw in `jupyter/nbconvert` allows a remote attacker to execute arbitrary JavaScript in the context of a user's browser. The vulnerability arises from improper sanitization of `text/vnd.mermaid` output during HTML export, enabling injection of malicious code when a user views an exported notebook from an untrusted source. This impacts Red Hat OpenShift AI, Migration Toolkit for Applications, and Red Hat Satellite, where `nbconvert` is utilized for notebook rendering. Users should avoid exporting or viewing untrusted notebooks as HTML to prevent the execution of arbitrary JavaScript. Migration Toolkit for Applications 8 Fix deferred mta/mta-solution-server-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-pipeline-runtime-datascience-cpu-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-pipeline-runtime-minimal-cpu-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-pipeline-runtime-pytorch-cuda-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-pipeline-runtime-pytorch-llmcompressor-cuda-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-pipeline-runtime-pytorch-rocm-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-pipeline-runtime-tensorflow-cuda-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-pipeline-runtime-tensorflow-rocm-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-th06-cpu-torch210-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-th06-cpu-torch291-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-th06-cuda130-torch210-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-th06-cuda130-torch291-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-th06-rocm64-torch291-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-workbench-jupyter-datascience-cpu-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-workbench-jupyter-minimal-cpu-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-workbench-jupyter-minimal-cuda-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-workbench-jupyter-minimal-rocm-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-workbench-jupyter-pytorch-cuda-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-workbench-jupyter-pytorch-llmcompressor-cuda-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-workbench-jupyter-pytorch-rocm-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-workbench-jupyter-tensorflow-cuda-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-workbench-jupyter-tensorflow-rocm-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-workbench-jupyter-trustyai-cpu-py312-rhel9 Red Hat Satellite 6 Fix deferred satellite/iop-advisor-engine-rhel9 https://www.cve.org/CVERecord?id=CVE-2026-6658 https://nvd.nist.gov/vuln/detail/CVE-2026-6658 https://huntr.com/bounties/47570290-3b26-4477-8cfa-fdef7db5aefe