{"id":"CVE-2021-21254","details":"CKEditor 5 is an open source rich text editor framework with a modular architecture. The CKEditor 5 Markdown plugin (@ckeditor/ckeditor5-markdown-gfm) before version 25.0.0 has a regex denial of service (ReDoS) vulnerability. The vulnerability allowed to abuse link recognition regular expression, which could cause a significant performance drop resulting in browser tab freeze. It affects all users using CKEditor 5 Markdown plugin at version \u003c= 24.0.0. The problem has been recognized and patched. The fix will be available in version 25.0.0.","aliases":["GHSA-hgmg-hhc8-g5wr"],"modified":"2026-07-09T14:06:37.686463Z","published":"2021-01-29T22:15:14.797Z","references":[{"type":"WEB","url":"https://www.npmjs.com/package/%40ckeditor/ckeditor5-markdown-gfm"},{"type":"ADVISORY","url":"https://github.com/ckeditor/ckeditor5/releases/tag/v25.0.0"},{"type":"ADVISORY","url":"https://github.com/ckeditor/ckeditor5/security/advisories/GHSA-hgmg-hhc8-g5wr"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/ckeditor/ckeditor5","events":[{"introduced":"0"},{"fixed":"0139bbe2732c2e1fd0225d857639521436c790b4"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"25.0.0"}],"cpe":"cpe:2.3:a:ckeditor:ckeditor5:*:*:*:*:*:*:*:*","source":["CPE_RANGE","REFERENCES"]}}],"versions":["v24.0.0","v19.1.1","v19.0.0","v18.0.0","v17.0.0","v16.0.0","v15.0.0","v12.3.1","v12.3.0","v12.2.0","v12.1.0","v12.0.0","v11.2.0","v11.1.1","v11.1.0","v11.0.0","v10.1.0","10.1.0","v10.0.0","v1.0.0-beta.4","v1.0.0-beta.2","v1.0.0-beta.1","v1.0.0-alpha.2","v1.0.0-alpha.1","v0.11.0","v0.10.0","v0.9.0","v0.7.0","v0.6.0","v0.5.0","v0.4.0","v0.3.0","v0.2.0","v0.1.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-21254.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}