{"id":"CVE-2021-26813","aliases":["DEBIAN-CVE-2021-26813","EUVD-2021-0118","GHSA-jr9p-r423-9m2r","PYSEC-2021-20","UBUNTU-CVE-2021-26813","openSUSE-SU-2021:0429-1","openSUSE-SU-2021:0451-1","openSUSE-SU-2024:11237-1","openSUSE-SU-2024:14146-1","openSUSE-SU-2026:12016-1"],"status":"published","title":"markdown2 Regular Expression Denial of Service","description":"markdown2 \u003e=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.","severity":{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"primary","from":"nvd"},"epss":{"day":"2026-11-11","score":0.02319,"percentile":0.83673,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-1333"],"published":"2021-03-03T15:17:41Z","modified":"2026-10-23T18:03:26Z","fixes":[{"ecosystem":"PyPI","package":"markdown2","fixed_in":["2.4.0"],"sources":["ghsa","osv"]},{"ecosystem":"Debian:12","package":"python-markdown2","fixed_in":["2.3.10-1.1"],"sources":["osv"]},{"ecosystem":"Debian:13","package":"python-markdown2","fixed_in":["2.3.10-1.1"],"sources":["osv"]},{"ecosystem":"Debian:14","package":"python-markdown2","fixed_in":["2.3.10-1.1"],"sources":["osv"]},{"ecosystem":"openSUSE:Leap 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SP2","package":"python-markdown2","fixed_in":["2.4.0-bp152.2.4.1"],"sources":["osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"markdown2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"1.0.1.18"},{"fixed":"2.4.0"}]}]},{"source":"osv","ecosystem":"Debian:12","package":"python-markdown2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.3.10-1.1"}]}]},{"source":"osv","ecosystem":"Debian:13","package":"python-markdown2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.3.10-1.1"}]}]},{"source":"osv","ecosystem":"Debian:14","package":"python-markdown2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.3.10-1.1"}]}]},{"source":"osv","ecosystem":"PyPI","package":"markdown2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"1.0.1.18"},{"fixed":"2.4.0"}]}],"versions":["1.0.1.18","1.0.1.19","1.1.0","1.1.1","1.2.0","1.3.0","1.3.1","1.4.0","1.4.1","1.4.2","2.0.0","2.0.1","2.1.0","2.2.0","2.2.1","2.2.2","2.2.3","2.3.0","2.3.1","2.3.10","2.3.2","2.3.3","2.3.4","2.3.5","2.3.6","2.3.7","2.3.8","2.3.9"]},{"source":"osv","ecosystem":"PyPI","package":"markdown2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"1.0.1.18"},{"fixed":"2.4.0"}]}],"versions":["1.0.1.18","1.0.1.19","1.1.0","1.1.1","1.2.0","1.3.0","1.3.1","1.4.0","1.4.1","1.4.2","2.0.0","2.0.1","2.1.0","2.2.0","2.2.1","2.2.2","2.2.3","2.3.0","2.3.1","2.3.2","2.3.3","2.3.4","2.3.5","2.3.6","2.3.7","2.3.8","2.3.9","2.3.10"]},{"source":"osv","ecosystem":"Ubuntu:20.04:LTS","package":"python-markdown2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.3.7-2"]},{"source":"osv","ecosystem":"Ubuntu:22.04:LTS","package":"python-markdown2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.3.10-1.1","2.4.1-1"]},{"source":"osv","ecosystem":"Ubuntu:24.04:LTS","package":"python-markdown2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.4.1-1","2.4.11-1"]},{"source":"osv","ecosystem":"Ubuntu:25.10","package":"python-markdown2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.4.11-1"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"python-markdown2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.5.4-3"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"python-markdown2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.4.11-1","2.5.4-2","2.5.4-3"]},{"source":"osv","ecosystem":"openSUSE:Leap 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SP2","package":"python-markdown2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.4.0-bp152.2.4.1"}]}]},{"source":"osv","ecosystem":"openSUSE:Tumbleweed","package":"python-markdown2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.4.0-2.4"}]}],"bundled":2},{"source":"osv","ecosystem":"openSUSE:Tumbleweed","package":"python-markdown2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.4.13-1.2"}]}],"bundled":2},{"source":"osv","ecosystem":"openSUSE:Tumbleweed","package":"python-markdown2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.5.5-1.3"}]}],"bundled":2}],"products":[{"vendor":"fedoraproject","product":"fedora"},{"vendor":"markdown2_project","product":"markdown2"}],"references":[{"url":"https://github.com/trentm/python-markdown2/pull/387","tags":["x_refsource_MISC","x_transferred","Exploit","Third Party Advisory","evidence","web","report"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/J752422YELXLMLZJPVJVKD2KKHHQRVEH/","tags":["vendor-advisory","x_refsource_FEDORA","x_transferred","web"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BRP5RN35JZTSJ3JT4722F447ZDK7LZS5/","tags":["vendor-advisory","x_refsource_FEDORA","x_transferred","web"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JTIX5UXRDJZJ57DO4V33ZNJTNKWGBQLY/","tags":["vendor-advisory","x_refsource_FEDORA","x_transferred","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-26813","tags":["advisory"]},{"url":"https://github.com/trentm/python-markdown2/commit/7b651260739647de5198323e0445b1618750c374","tags":["web"]},{"url":"https://github.com/advisories/GHSA-jr9p-r423-9m2r","tags":["advisory"]},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/markdown2/PYSEC-2021-20.yaml","tags":["web"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/BRP5RN35JZTSJ3JT4722F447ZDK7LZS5","tags":["web"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/J752422YELXLMLZJPVJVKD2KKHHQRVEH","tags":["web"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/JTIX5UXRDJZJ57DO4V33ZNJTNKWGBQLY","tags":["web"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2021-26813","tags":["advisory"]},{"url":"https://github.com/trentm/python-markdown2","tags":["package"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/BRP5RN35JZTSJ3JT4722F447ZDK7LZS5/","tags":["web"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/JTIX5UXRDJZJ57DO4V33ZNJTNKWGBQLY/","tags":["web"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/J752422YELXLMLZJPVJVKD2KKHHQRVEH/","tags":["web"]},{"url":"https://ubuntu.com/security/CVE-2021-26813","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2021-26813","tags":["report"]},{"url":"https://lists.opensuse.org/archives/list/security-announce@lists.opensuse.org/thread/3VPKRS46KKKFGLEDJJ7ZX2EZVNE5567H/","tags":["advisory"]},{"url":"https://bugzilla.suse.com/1171379","tags":["report"]},{"url":"https://bugzilla.suse.com/1181270","tags":["report"]},{"url":"https://bugzilla.suse.com/1183171","tags":["report"]},{"url":"https://www.suse.com/security/cve/CVE-2021-26813","tags":["web"]},{"url":"https://lists.opensuse.org/archives/list/security-announce@lists.opensuse.org/thread/4AZ6CPAAHWZ74LZWHDSAXWA6O2HYCKU3/","tags":["advisory"]},{"url":"","tags":["advisory"]},{"url":"https://www.suse.com/security/cve/CVE-2018-5773","tags":["web"]}],"sources":{"cve":[{"id":"CVE-2021-26813","description":"markdown2 \u003e=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.","status":"published","published":"2021-03-03T15:17:41Z","modified":"2024-08-03T20:33:41.236Z","updated_at":"2026-11-02T14:32:57.368269Z"}],"euvd":[{"id":"EUVD-2021-0118","description":"markdown2 \u003e=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.","status":"published","published":"2021-03-03T15:17:41Z","modified":"2024-08-03T20:33:41Z","updated_at":"2026-11-03T03:24:50.84326Z"}],"ghsa":[{"id":"GHSA-jr9p-r423-9m2r","title":"markdown2 Regular Expression Denial of Service ","description":"markdown2 \u003e=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.","status":"published","published":"2021-06-02T21:44:28Z","modified":"2024-09-30T20:15:07Z","cvss":[{"version":"4.0","score":8.7,"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","level":"high"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-1333"],"updated_at":"2026-11-02T14:38:07.852618Z"}],"nvd":[{"id":"CVE-2021-26813","description":"markdown2 \u003e=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.","status":"published","published":"2021-03-03T16:15:13.197Z","modified":"2026-06-17T03:43:49.013Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"primary"},{"version":"2.0","score":5,"vector":"AV:N/AC:L/Au:N/C:N/I:N/A:P","level":"medium","assessor":"primary"}],"cwes":["CWE-1333"],"updated_at":"2026-11-02T14:06:50.399901Z"}],"osv":[{"id":"CVE-2021-26813","description":"markdown2 \u003e=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.","status":"published","published":"2021-03-03T16:15:13.197Z","modified":"2026-10-20T10:54:34.501695461Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:44:18.778776Z"},{"id":"DEBIAN-CVE-2021-26813","description":"markdown2 \u003e=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.","status":"published","published":"2021-03-03T16:15:13.197Z","modified":"2026-10-23T18:03:26.072429297Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:45:34.637046Z"},{"id":"GHSA-jr9p-r423-9m2r","title":"markdown2 Regular Expression Denial of Service ","description":"markdown2 \u003e=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.","status":"published","published":"2021-06-02T21:44:28Z","modified":"2025-02-21T05:30:49.729149Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"},{"version":"4.0","score":8.7,"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","level":"high"}],"cwes":["CWE-1333"],"updated_at":"2026-11-02T15:46:50.687609Z"},{"id":"UBUNTU-CVE-2021-26813","description":"markdown2 \u003e=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.","status":"published","published":"2021-03-03T16:15:00Z","modified":"2026-10-17T12:57:12.382213228Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:54:26.779273Z"},{"id":"openSUSE-SU-2021:0429-1","title":"Security update for python-markdown2","description":"This update for python-markdown2 fixes the following issues:\n\nUpdate to 2.4.0 (boo#1181270):\n\n  - [pull #377] Fixed bug breaking strings elements in metadata lists\n  - [pull #380] When rendering fenced code blocks, also add the\n    language-LANG class\n  - [pull #387] Regex DoS fixes (CVE-2021-26813, boo#1183171)\n\n- Switch off failing tests (gh#trentm/python-markdown2#388),\n  ignore failing test suite.\n\nupdate to 2.3.9:\n\n  - [pull #335] Added header support for wiki tables\n  - [pull #336] Reset _toc when convert is run\n  - [pull #353] XSS fix\n  - [pull #350] XSS fix\n\n- Add patch to fix unsanitized input for cross-site scripting (boo#1171379)\n","status":"published","published":"2021-03-16T17:08:32Z","modified":"2026-02-04T02:48:36.636157Z","updated_at":"2026-11-02T16:58:31.879684Z"},{"id":"openSUSE-SU-2021:0451-1","title":"Security update for python-markdown2","description":"This update for python-markdown2 fixes the following issues:\n\nUpdate to 2.4.0 (boo#1181270):\n\n  - [pull #377] Fixed bug breaking strings elements in metadata lists\n  - [pull #380] When rendering fenced code blocks, also add the\n    language-LANG class\n  - [pull #387] Regex DoS fixes (CVE-2021-26813, boo#1183171)\n\n- Switch off failing tests (gh#trentm/python-markdown2#388),\n  ignore failing test suite.\n\nupdate to 2.3.9:\n\n  - [pull #335] Added header support for wiki tables\n  - [pull #336] Reset _toc when convert is run\n  - [pull #353] XSS fix\n  - [pull #350] XSS fix\n\n- Add patch to fix unsanitized input for cross-site scripting (boo#1171379)\n\nThis update was imported from the openSUSE:Leap:15.2:Update update project.","status":"published","published":"2021-03-19T23:06:22Z","modified":"2026-02-04T03:22:01.96991Z","updated_at":"2026-11-02T16:58:31.879684Z"},{"id":"openSUSE-SU-2024:11237-1","title":"python36-markdown2-2.4.0-2.4 on GA media","description":"These are all security issues fixed in the python36-markdown2-2.4.0-2.4 package on the GA media of openSUSE Tumbleweed.","status":"published","published":"2024-06-15T00:00:00Z","modified":"2026-02-04T03:55:06.870993Z","updated_at":"2026-11-02T16:58:34.894275Z"},{"id":"openSUSE-SU-2024:14146-1","title":"python310-markdown2-2.4.13-1.2 on GA media","description":"These are all security issues fixed in the python310-markdown2-2.4.13-1.2 package on the GA media of openSUSE Tumbleweed.","status":"published","published":"2024-07-12T00:00:00Z","modified":"2026-02-04T02:31:20.860257Z","updated_at":"2026-11-02T16:58:36.662953Z"},{"id":"openSUSE-SU-2026:12016-1","title":"python313-markdown2-2.5.5-1.3 on GA media","description":"These are all security issues fixed in the python313-markdown2-2.5.5-1.3 package on the GA media of openSUSE Tumbleweed.","status":"published","published":"2026-10-04T00:00:00Z","modified":"2026-10-05T10:15:56.076614494Z","updated_at":"2026-11-02T16:58:40.245664Z"},{"id":"PYSEC-2021-20","description":"markdown2 \u003e=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.","status":"published","published":"2021-03-03T16:15:00Z","modified":"2023-11-08T04:05:22.342158Z","updated_at":"2026-11-02T15:52:52.682031Z"}]}}