{"id":"CVE-2026-49851","aliases":["GHSA-qcq2-496w-v96p","PYSEC-2026-2652"],"url":"https://o3.security/vulnerability/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.","published":"2026-06-24T17:05:33.602Z","modified":"2026-08-12T03:51:22.522838518Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"mistune","fixedVersion":"3.3.0"}],"fix":null,"references":[{"type":"WEB","url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-49851.json"},{"type":"ADVISORY","url":"https://access.redhat.com/security/cve/CVE-2026-49851"},{"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"},{"type":"REPORT","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2492304"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:22.522838518Z"}}