{"id":"CVE-2021-26813","aliases":["GHSA-jr9p-r423-9m2r","PYSEC-2021-20"],"url":"https://o3.security/vulnerability/CVE-2021-26813","summary":"markdown2 Regular Expression Denial of Service ","details":"markdown2 >=1.0.1.18, fixed in 2.4.0, is affected by a regular expression denial of service vulnerability. If an attacker provides a malicious string, it can make markdown2 processing difficult or delayed for an extended period of time.","published":"2021-03-03T16:15:13.197Z","modified":"2026-07-08T05:58:58.945182290Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"PyPI","name":"markdown2","fixedVersion":"2.4.0"}],"fix":{"url":"https://github.com/trentm/python-markdown2/pull/387","label":"trentm/python-markdown2#387"},"references":[{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BRP5RN35JZTSJ3JT4722F447ZDK7LZS5/"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/J752422YELXLMLZJPVJVKD2KKHHQRVEH/"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JTIX5UXRDJZJ57DO4V33ZNJTNKWGBQLY/"},{"type":"EVIDENCE","url":"https://github.com/trentm/python-markdown2/pull/387"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-08T05:58:58.945182290Z"}}