{"id":"UBUNTU-CVE-2026-44899","details":"Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, the Image directive plugin validates the :width: and :height: options with a regex compiled as _num_re = re.compile(r\"^\\d+(?:\\.\\d*)?\"). When the validated value is not a plain integer, render_block_image() inserts it directly into a style=\"width:...;\" or style=\"height:...;\" attribute. Because the value was accepted by the prefix-only regex, any CSS after the leading digits reaches the style= attribute verbatim and without escaping. This vulnerability is fixed in 3.2.1.","modified":"2026-05-29T18:00:45.128088209Z","published":"2026-05-26T21:16:00Z","upstream":["CVE-2026-44899"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-44899"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-44899"},{"type":"REPORT","url":"https://github.com/lepture/mistune/releases/tag/v3.2.1"},{"type":"REPORT","url":"https://github.com/lepture/mistune/security/advisories/GHSA-ccfx-mfmx-2fx9"}],"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_name":"python3-mistune","binary_version":"0.7.1-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-44899.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_name":"python3-mistune","binary_version":"0.8.3-2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-44899.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_version":"0.8.4-2","binary_name":"python3-mistune"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-44899.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-2026-44899.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_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-2026-44899.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_version":"3.0.2-1","binary_name":"python3-mistune"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-44899.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-2026-44899.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-2026-44899.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-2026-44899.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":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-44899.json"}},{"package":{"name":"mistune0","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/mistune0?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.8.4-4","0.8.4-5","0.8.4-6"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-mistune0","binary_version":"0.8.4-6"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-44899.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"},{"type":"Ubuntu","score":"medium"}]}