{"cve":"CVE-2026-49851","nvd":{"published":"2026-06-24T18:17:18.937","modified":"2026-10-25T22:10:00.150","status":"Deferred","description":"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.","cvss_v4":{"vector":"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","score":8.7},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":["CWE-400","CWE-407","CWE-770","CWE-1333"],"references":["https://github.com/lepture/mistune/security/advisories/GHSA-qcq2-496w-v96p","https://access.redhat.com/errata/RHSA-2026:60520","https://access.redhat.com/security/cve/CVE-2026-49851","https://bugzilla.redhat.com/show_bug.cgi?id=2492304","https://github.com/lepture/mistune/security/advisories/GHSA-qcq2-496w-v96p"],"products":[],"source":"nvd","synced_at":"2026-10-25T23:44:33.281319194+00:00"},"epss":{"cve":"CVE-2026-49851","score":0.0063,"percentile":0.49889,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-qcq2-496w-v96p","url":"https://osv.dev/vulnerability/GHSA-qcq2-496w-v96p","summary":" Mistune: Potential DoS via quadratic-time parsing in parse_link_text","modified":"2026-09-10T03:51:11.807497442Z","packages":[{"ecosystem":"PyPI","name":"mistune","purl":"pkg:pypi/mistune","ranges":["<3.3.0"],"fixed":["3.3.0"]}]},{"id":"PYSEC-2026-2652","url":"https://osv.dev/vulnerability/PYSEC-2026-2652","summary":" Mistune: Potential DoS via quadratic-time parsing in parse_link_text","modified":"2026-07-13T16:31:51.196638693Z","packages":[{"ecosystem":"PyPI","name":"mistune","purl":"pkg:pypi/mistune","ranges":["<3.3.0"],"fixed":["3.3.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}