Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-07-08T16:23:21 mistune: Mistune: Denial of Service via crafted Markdown document with reference-link definitions 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H CWE-606

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a Markdown document containing many repeated or distinct reference-link definitions causes quadratic work in src/mistune/block_parser.py and the ref_links environment dictionary handling, allowing denial of service through CPU exhaustion. This issue is fixed in version 3.3.0.

A flaw was found in Mistune, a Python Markdown parser. A remote attacker could exploit this vulnerability by providing a specially crafted Markdown document containing numerous repeated or distinct reference-link definitions. This can lead to excessive processing, causing CPU exhaustion and a denial of service (DoS) for the affected system.

A flaw was found in Mistune, a Python Markdown parser. An attacker who can supply Markdown for parsing could exploit this vulnerability by providing a specially crafted document containing numerous repeated or distinct reference-link definitions. This triggers excessive CPU consumption during parsing, which may render affected applications unresponsive and result in a denial of service. Red Hat uses PR:L because delivering the crafted Markdown document document to Mistune will require authenticated access in affected products, platform login/RBAC prevents unauthenticated remote submission in default deployments. The upstream PR:N score assumes any Internet-facing app parsing untrusted Markdown without authentication. To mitigate this issue, avoid processing untrusted Markdown documents with affected Red Hat products. Restricting the input sources to trusted content can reduce the risk of a denial of service attack. 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 Fix deferred satellite/iop-advisor-engine-rhel9 https://www.cve.org/CVERecord?id=CVE-2026-59928 https://nvd.nist.gov/vuln/detail/CVE-2026-59928 https://github.com/lepture/mistune/commit/2b04d7ba341c16ac78fe82d3076bdd5c3de87c69 https://github.com/lepture/mistune/releases/tag/v3.3.0 https://github.com/lepture/mistune/security/advisories/GHSA-ffq3-xpv3-j92q