{"id":"CVE-2021-20185","aliases":["BIT-moodle-2021-20185","EUVD-2022-3488","GHSA-c3j6-33r4-89q3","UBUNTU-CVE-2021-20185"],"status":"published","title":"Moodle Client side denial of service via personal message","description":"It was found in Moodle before version 3.10.1, 3.9.4, 3.8.7 and 3.5.16 that messaging did not impose a character limit when sending messages, which could result in client-side (browser) denial of service for users receiving very large messages.","severity":{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium","assessor":"primary","from":"nvd"},"epss":{"day":"2026-11-10","score":0.01394,"percentile":0.72605,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-400","CWE-770"],"published":"2021-01-28T19:01:04Z","modified":"2026-10-24T10:30:25Z","fixes":[{"ecosystem":"Packagist","package":"moodle/moodle","fixed_in":["3.5.16","3.8.7","3.9.4","3.10.1"],"sources":["ghsa","osv"]},{"ecosystem":"Bitnami","package":"moodle","fixed_in":["3.5.16","3.8.7","3.9.4","3.10.1"],"sources":["osv"]}],"affected":[{"source":"ghsa","ecosystem":"Packagist","package":"moodle/moodle","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.5"},{"fixed":"3.5.16"}]}]},{"source":"ghsa","ecosystem":"Packagist","package":"moodle/moodle","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.8"},{"fixed":"3.8.7"}]}]},{"source":"ghsa","ecosystem":"Packagist","package":"moodle/moodle","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.9"},{"fixed":"3.9.4"}]}]},{"source":"ghsa","ecosystem":"Packagist","package":"moodle/moodle","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.10"},{"fixed":"3.10.1"}]}]},{"source":"osv","ecosystem":"Bitnami","package":"moodle","ranges":[{"type":"SEMVER","events":[{"introduced":"3.5.0"},{"fixed":"3.5.16"},{"introduced":"3.8.0"},{"fixed":"3.8.7"},{"introduced":"3.9.0"},{"fixed":"3.9.4"},{"introduced":"3.10.0"},{"fixed":"3.10.1"}]}]},{"source":"osv","ecosystem":"Packagist","package":"moodle/moodle","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.5"},{"fixed":"3.5.16"}]}],"versions":["v3.5.0","v3.5.0-beta","v3.5.0-rc1","v3.5.1","v3.5.10","v3.5.11","v3.5.12","v3.5.13","v3.5.14","v3.5.15","v3.5.2","v3.5.3","v3.5.4","v3.5.5","v3.5.6","v3.5.7","v3.5.8","v3.5.9"]},{"source":"osv","ecosystem":"Packagist","package":"moodle/moodle","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.8"},{"fixed":"3.8.7"}]}],"versions":["v3.8.0","v3.8.0-beta","v3.8.0-rc1","v3.8.1","v3.8.2","v3.8.3","v3.8.4","v3.8.5","v3.8.6"]},{"source":"osv","ecosystem":"Packagist","package":"moodle/moodle","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.9"},{"fixed":"3.9.4"}]}],"versions":["v3.9.0","v3.9.0-beta","v3.9.0-rc1","v3.9.0-rc2","v3.9.0-rc3","v3.9.1","v3.9.2","v3.9.3"]},{"source":"osv","ecosystem":"Packagist","package":"moodle/moodle","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.10"},{"fixed":"3.10.1"}]}],"versions":["v3.10.0","v3.10.0-beta","v3.10.0-rc1","v3.10.0-rc2"]},{"source":"osv","ecosystem":"Ubuntu:Pro:16.04:LTS","package":"moodle","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.7.9+dfsg-1","2.7.10+dfsg-1","2.7.11+dfsg-1","2.7.11+dfsg-2","2.7.12+dfsg-1","3.0.3+dfsg-0ubuntu1","3.0.3+dfsg-0ubuntu1+esm1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:18.04:LTS","package":"moodle","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.0.3+dfsg-0ubuntu1","3.0.3+dfsg-0ubuntu1+esm1"]}],"products":[{"vendor":"moodle","product":"moodle"}],"references":[{"url":"https://moodle.org/mod/forum/discuss.php?d=417168","tags":["x_refsource_MISC","x_transferred","Patch","Vendor Advisory","advisory","fix","web","report"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-20185","tags":["web","advisory"]},{"url":"https://github.com/advisories/GHSA-c3j6-33r4-89q3"},{"url":"https://github.com/moodle/moodle","tags":["package"]},{"url":"https://ubuntu.com/security/CVE-2021-20185","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2021-20185","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2021-20185","description":"It was found in Moodle before version 3.10.1, 3.9.4, 3.8.7 and 3.5.16 that messaging did not impose a character limit when sending messages, which could result in client-side (browser) denial of service for users receiving very large messages.","status":"published","published":"2021-01-28T19:01:04Z","modified":"2024-08-03T17:30:07.687Z","cwes":["CWE-400"],"updated_at":"2026-11-02T14:32:55.19484Z"}],"euvd":[{"id":"EUVD-2022-3488","description":"It was found in Moodle before version 3.10.1, 3.9.4, 3.8.7 and 3.5.16 that messaging did not impose a character limit when sending messages, which could result in client-side (browser) denial of service for users receiving very large messages.","status":"published","published":"2021-01-28T19:01:04Z","modified":"2024-08-03T17:30:07Z","updated_at":"2026-11-03T03:25:09.355483Z"}],"ghsa":[{"id":"GHSA-c3j6-33r4-89q3","title":"Moodle Client side denial of service via personal message","description":"It was found in Moodle before version 3.10.1, 3.9.4, 3.8.7 and 3.5.16 that messaging did not impose a character limit when sending messages, which could result in client-side (browser) denial of service for users receiving very large messages.","status":"published","published":"2022-05-24T17:40:31Z","modified":"2024-04-23T23:38:02Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"cwes":["CWE-400","CWE-770"],"updated_at":"2026-11-02T14:37:44.867253Z"}],"nvd":[{"id":"CVE-2021-20185","description":"It was found in Moodle before version 3.10.1, 3.9.4, 3.8.7 and 3.5.16 that messaging did not impose a character limit when sending messages, which could result in client-side (browser) denial of service for users receiving very large messages.","status":"published","published":"2021-01-28T20:15:13.133Z","modified":"2026-06-17T03:33:26.197Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium","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-400","CWE-770"],"updated_at":"2026-11-02T14:06:49.660551Z"}],"osv":[{"id":"CVE-2021-20185","description":"It was found in Moodle before version 3.10.1, 3.9.4, 3.8.7 and 3.5.16 that messaging did not impose a character limit when sending messages, which could result in client-side (browser) denial of service for users receiving very large messages.","status":"published","published":"2021-01-28T20:15:13.133Z","modified":"2026-10-24T10:30:25.623295162Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"updated_at":"2026-11-02T15:44:17.663289Z"},{"id":"GHSA-c3j6-33r4-89q3","title":"Moodle Client side denial of service via personal message","description":"It was found in Moodle before version 3.10.1, 3.9.4, 3.8.7 and 3.5.16 that messaging did not impose a character limit when sending messages, which could result in client-side (browser) denial of service for users receiving very large messages.","status":"published","published":"2022-05-24T17:40:31Z","modified":"2024-04-24T00:11:40.187981Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"cwes":["CWE-400","CWE-770"],"updated_at":"2026-11-02T15:46:44.571161Z"},{"id":"UBUNTU-CVE-2021-20185","description":"It was found in Moodle before version 3.10.1, 3.9.4, 3.8.7 and 3.5.16 that messaging did not impose a character limit when sending messages, which could result in client-side (browser) denial of service for users receiving very large messages.","status":"published","published":"2021-01-28T20:15:00Z","modified":"2026-09-23T18:46:09.445245049Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"updated_at":"2026-11-02T15:54:25.728622Z"},{"id":"BIT-moodle-2021-20185","description":"It was found in Moodle before version 3.10.1, 3.9.4, 3.8.7 and 3.5.16 that messaging did not impose a character limit when sending messages, which could result in client-side (browser) denial of service for users receiving very large messages.","status":"published","published":"2024-03-06T11:11:15.258Z","modified":"2026-09-08T08:48:14.728024573Z","updated_at":"2026-11-02T15:28:33.469426Z"}]}}