{"id":"UBUNTU-CVE-2026-49851","details":"Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, Mistune is vulnerable to a CPU exhaustion DoS due to superlinear (approximately O(n²)) behavior in parse_link_text. When parsing Markdown containing many consecutive [ characters, parse_link_text repeatedly scans the input using a regex search inside a loop. Each iteration re-scans a large portion of the remaining string, resulting in quadratic-time behavior. An attacker-controlled Markdown input can therefore trigger excessive CPU usage with a very small payload. This vulnerability is fixed in 3.3.0.","modified":"2026-06-30T18:18:17.317096999Z","published":"2026-06-24T18:17:00Z","upstream":["CVE-2026-49851"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-49851"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-49851"},{"type":"REPORT","url":"https://github.com/lepture/mistune/security/advisories/GHSA-qcq2-496w-v96p"}],"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-2026-49851.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_version":"0.8.3-2","binary_name":"python-mistune"},{"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-2026-49851.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-2026-49851.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-2026-49851.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-2026-49851.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_name":"python3-mistune","binary_version":"3.1.3-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-49851.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-2026-49851.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"type":"Ubuntu","score":"medium"}]}