{"id":"UBUNTU-CVE-2021-21391","details":"CKEditor 5 provides a WYSIWYG editing solution. This CVE affects the following npm packages: ckeditor5-engine, ckeditor5-font, ckeditor5-image, ckeditor5-list, ckeditor5-markdown-gfm, ckeditor5-media-embed, ckeditor5-paste-from-office, and ckeditor5-widget. Following an internal audit, a regular expression denial of service (ReDoS) vulnerability has been discovered in multiple CKEditor 5 packages. The vulnerability allowed to abuse particular regular expressions, which could cause a significant performance drop resulting in a browser tab freeze. It affects all users using the CKEditor 5 packages listed above at version \u003c= 26.0.0. The problem has been recognized and patched. The fix will be available in version 27.0.0.","modified":"2026-01-20T17:21:31.493249Z","published":"2021-04-29T01:15:00Z","upstream":["CVE-2021-21391"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2021-21391"},{"type":"REPORT","url":"https://www.npmjs.com/package/@ckeditor/ckeditor5-markdown-gfm"},{"type":"REPORT","url":"https://www.npmjs.com/package/@ckeditor/ckeditor5-engine"},{"type":"REPORT","url":"https://www.npmjs.com/package/@ckeditor/ckeditor5-image"},{"type":"REPORT","url":"https://www.npmjs.com/package/@ckeditor/ckeditor5-media-embed"},{"type":"REPORT","url":"https://github.com/ckeditor/ckeditor5/security/advisories/GHSA-3rh3-wfr4-76mj"},{"type":"REPORT","url":"https://www.npmjs.com/package/@ckeditor/ckeditor5-list"},{"type":"REPORT","url":"https://www.npmjs.com/package/@ckeditor/ckeditor5-font"},{"type":"REPORT","url":"https://www.npmjs.com/package/@ckeditor/ckeditor5-paste-from-office"},{"type":"REPORT","url":"https://www.npmjs.com/package/@ckeditor/ckeditor5-widget"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2021-21391"}],"affected":[{"package":{"name":"ckeditor3","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/ckeditor3@3.6.6.1+dfsg-1?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.6.6.1+dfsg-1"],"ecosystem_specific":{"binaries":[{"binary_name":"ckeditor3","binary_version":"3.6.6.1+dfsg-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-21391.json"}},{"package":{"name":"ckeditor3","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/ckeditor3@3.6.6.1+dfsg-4?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.6.6.1+dfsg-3","3.6.6.1+dfsg-4"],"ecosystem_specific":{"binaries":[{"binary_name":"ckeditor3","binary_version":"3.6.6.1+dfsg-4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-21391.json"}},{"package":{"name":"ckeditor3","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/ckeditor3@3.6.6.1+dfsg-7?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.6.6.1+dfsg-7"],"ecosystem_specific":{"binaries":[{"binary_name":"ckeditor3","binary_version":"3.6.6.1+dfsg-7"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-21391.json"}},{"package":{"name":"ckeditor3","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/ckeditor3@3.6.6.1+dfsg-7?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.6.6.1+dfsg-7"],"ecosystem_specific":{"binaries":[{"binary_name":"ckeditor3","binary_version":"3.6.6.1+dfsg-7"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-21391.json"}}],"schema_version":"1.7.3","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H"},{"type":"Ubuntu","score":"medium"}]}