{"id":"CVE-2026-49851","summary":"Mistune: Potential DoS via quadratic-time parsing in parse_link_text","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.","aliases":["GHSA-qcq2-496w-v96p"],"modified":"2026-06-25T04:04:15.865010871Z","published":"2026-06-24T17:05:33.602Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/49xxx/CVE-2026-49851.json","cwe_ids":["CWE-400","CWE-407","CWE-770"],"cna_assigner":"GitHub_M"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/49xxx/CVE-2026-49851.json"},{"type":"ADVISORY","url":"https://github.com/lepture/mistune/security/advisories/GHSA-qcq2-496w-v96p"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-49851"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/lepture/mistune","events":[{"introduced":"0"},{"fixed":"15c3b79325125272263d7d42492ec8f757447191"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"3.3.0"}],"source":"AFFECTED_FIELD"}}],"versions":["v3.2.1","v3.2.0","v3.1.4","v3.1.3","v3.1.2","v3.1.1","v3.1.0","v3.0.1","v3.0.0","v3.0.0rc5","v3.0.0rc4","v3.0.0rc3","v3.0.0rc2","v3.0.0rc1","v3.0.0a3","v3.0.0a2","v3.0.0a1","v2.0.2","v2.0.1","v2.0.0","v2.0.0rc1","v2.0.0a6","v2.0.0a5","v2.0.0a4","v2.0.0a3","v2.0.0a2","v2.0.0a1","v0.8.4","v0.8.3","v0.8.2","v0.8.1","v0.8","v0.7.4","v0.7.3","v0.7.2","v0.7.1","v0.7","v0.6","v0.5.1","v0.5","v0.4.1","v0.4","v0.3.1","v0.3.0","v0.2.0","v0.1.0"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/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"}]}