{"id":"UBUNTU-CVE-2026-44898","details":"Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, render_toc_ul() builds a \u003cul\u003e table-of-contents tree from a list of (level, id, text) tuples. Both the id value (used as href=\"#\u003cid\u003e\") and the text value (used as the visible link label) are inserted into \u003ca\u003e tags via a plain Python format string — with no HTML escaping applied to either value. When heading IDs are derived from user-supplied heading text (the standard use-case for readable slug anchors), an attacker can craft a heading whose text breaks out of the href=\"#...\" attribute context, injecting arbitrary HTML tags including \u003cscript\u003e blocks directly into the rendered TOC. This vulnerability is fixed in 3.2.1.","modified":"2026-05-27T19:15:29.083994863Z","published":"2026-05-26T21:16:00Z","upstream":["CVE-2026-44898"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-44898"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-44898"},{"type":"REPORT","url":"https://github.com/lepture/mistune/releases/tag/v3.2.1"},{"type":"REPORT","url":"https://github.com/lepture/mistune/security/advisories/GHSA-6269-cqxg-mhhv"}],"affected":[{"package":{"name":"mistune","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/mistune?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.6-2","0.7.1-1"],"ecosystem_specific":{"binaries":[{"binary_name":"python-mistune","binary_version":"0.7.1-1"},{"binary_version":"0.7.1-1","binary_name":"python3-mistune"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-44898.json"}},{"package":{"name":"mistune","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/mistune?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.7.4-1","0.8-1","0.8.1-1","0.8.3-2"],"ecosystem_specific":{"binaries":[{"binary_name":"python-mistune","binary_version":"0.8.3-2"},{"binary_version":"0.8.3-2","binary_name":"python3-mistune"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-44898.json"}},{"package":{"name":"mistune","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/mistune?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.8.4-1","0.8.4-2"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-mistune","binary_version":"0.8.4-2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-44898.json"}},{"package":{"name":"mistune","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/mistune?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.8.4-4","0.8.4-5","2.0.0-1+really0.8.4-1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-mistune","binary_version":"2.0.0-1+really0.8.4-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-44898.json"}},{"package":{"name":"mistune0","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/mistune0?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.8.4-1","0.8.4-2"],"ecosystem_specific":{"binaries":[{"binary_version":"0.8.4-2","binary_name":"python3-mistune0"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-44898.json"}},{"package":{"name":"mistune","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/mistune?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.4-2","3.0.2-1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-mistune","binary_version":"3.0.2-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-44898.json"}},{"package":{"name":"mistune0","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/mistune0?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.8.4-2"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-mistune0","binary_version":"0.8.4-2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-44898.json"}},{"package":{"name":"mistune","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/mistune?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.0.2-2","3.1.3-1"],"ecosystem_specific":{"binaries":[{"binary_version":"3.1.3-1","binary_name":"python3-mistune"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-44898.json"}},{"package":{"name":"mistune0","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/mistune0?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.8.4-4"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-mistune0","binary_version":"0.8.4-4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-44898.json"}},{"package":{"name":"mistune","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/mistune?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.1.3-1","3.1.4-1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-mistune","binary_version":"3.1.4-1"}]},"database_specific":{"source":"h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