Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-07-08T16:16:15 mistune: Mistune: Cross-Site Scripting via unescaped HTML class attribute in Admonition directive 5.4 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N CWE-79

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, render_admonition() in src/mistune/directives/admonition.py concatenates the Admonition directive :class: option into the HTML class attribute without escaping, allowing attribute injection and cross-site scripting even when HTMLRenderer escape mode is enabled. This issue is fixed in version 3.2.1.

A flaw was found in Mistune, a Python Markdown parser. The `render_admonition()` function in the Admonition directive concatenates user-controlled input into the HTML class attribute without proper escaping. This vulnerability allows for attribute injection and Cross-Site Scripting (XSS) attacks, even when the HTMLRenderer escape mode is enabled. A remote attacker could exploit this by providing specially crafted input, leading to the execution of arbitrary script code in the user's browser.

This Moderate flaw in the Mistune Markdown parser allows for Cross-Site Scripting (XSS) due to improper sanitization of user-controlled input within the Admonition directive's class attribute. An attacker could exploit this by providing specially crafted Markdown content, leading to the execution of arbitrary script code in a user's browser when the content is rendered. This vulnerability requires user interaction with malicious content for successful exploitation. To mitigate this issue, avoid processing untrusted or unvalidated Markdown content with affected versions of the Mistune library. Implement robust input validation and sanitization for any user-provided Markdown before rendering to prevent the injection of malicious attributes or scripts. 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 OpenShift Container Platform 4 Fix deferred python-mistune Red Hat Satellite 6 Under investigation satellite/iop-advisor-engine-rhel9 https://www.cve.org/CVERecord?id=CVE-2026-59926 https://nvd.nist.gov/vuln/detail/CVE-2026-59926 https://github.com/lepture/mistune/commit/a3cb6e5655308797e8be021d6c7b5bab13cbace2 https://github.com/lepture/mistune/releases/tag/v3.2.1 https://github.com/lepture/mistune/security/advisories/GHSA-g97x-gvcm-x72h