Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-07-08T16:20:38 mistune: Mistune: Cross-site scripting via incomplete URL scheme filtering 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N CWE-79

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, the safe_url filter in src/mistune/renderers/html.py blocks only javascript:, vbscript:, file:, and data: schemes, allowing legacy or chained schemes such as feed:, view-source:, jar:, livescript:, mocha:, ms-its:, mk:, and res: to reach rendered href and src attributes and potentially execute script in affected user agents. This issue is fixed in version 3.3.0.

A flaw was found in Mistune, a Python Markdown parser. The `safe_url` filter, intended to prevent malicious Uniform Resource Locators (URLs), did not adequately block all potentially harmful schemes. This oversight allows an attacker to embed specially crafted URLs using legacy or chained schemes within rendered HTML attributes. Consequently, a remote attacker could exploit this to execute arbitrary script code in a user's browser, leading to a Cross-Site Scripting (XSS) vulnerability.

This Moderate-impact flaw in Mistune, a Python Markdown parser, allows for Cross-Site Scripting (XSS) due to insufficient filtering of URL schemes. Exploitation requires a user to process specially crafted Markdown content, which could lead to arbitrary script execution in the user browser. Red Hat products that utilize Mistune to render untrusted Markdown input are susceptible to this vulnerability. No dedicated mitigation is available beyond upgrading to Mistune 3.3.0 or later, which fully blocks all dangerous URL schemes in the safe_url filter. As a temporary workaround, applications can wrap Mistune output in an additional allow-list-based URL sanitizer before rendering untrusted Markdown content, or avoid rendering Markdown from untrusted/attacker-controlled sources. 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-2026-59929 https://nvd.nist.gov/vuln/detail/CVE-2026-59929 https://github.com/lepture/mistune/commit/c7101fcbb6e8790e8e39157c5ca2238fc6dd6cbc https://github.com/lepture/mistune/releases/tag/v3.3.0 https://github.com/lepture/mistune/security/advisories/GHSA-qfrw-5rxm-mhh2